Instrument Information
| INSTRUMENT_TYPE | "RADIO SCIENCE" |
| INSTRUMENT_DESC |
Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " The Ultraviolet Imaging Spectrograph Subsystem (UVIS) is a set of telescopes used to measure ultraviolet light from the Saturn system's atmospheres, rings, and surfaces. The UVIS will also observe the fluctuations of starlight and sunlight as the sun and stars move behind the rings and the atmospheres of Titan and Saturn, and it will determine the atmospheric concentrations of hydrogen and deuterium. The following is a brief description of the components of the UVIS. For a more detailed description, see [ESPOSITOETAL2005] and contained in the DOCUMENT directory of this archive (pending permission). The UVIS has two spectrographic channels: the extreme ultraviolet channel and the far ultraviolet channel. The ultraviolet channels are built into weight-relieved aluminum cases, and each contains a reflecting telescope, a concave grating spectrometer, and an imaging, pulse-counting detector. The UVIS also includes a high-speed photometer channel, a hydrogen-deuterium absorption cell channel, and an electronic and control subassembly. The extreme ultraviolet channel (EUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn. The EUV consists of a telescope with a three-position slit changer, a baffle system, and a spectrograph with a CODACON microchannel plate detector and associated electronics. The telescope consists of an off-axis parabolic section with a focal length of 100 mm, a 22 mm by 30 mm aperture, and a baffle with a field of view of 3.67 degrees by 0.34 degrees. A precision mechanism positions one of the three entrance slits at the focal plane of the telescope, each translating to a different spectral resolution. The spectrograph uses an aberration-corrected toroidal grating that focuses the spectrum onto an imaging microchannel plate detector to achieve both high sensitivity and spatial resolution along the entrance slit. The microchannel plate detector electronics consist of a low-voltage power supply, a programmable high-voltage power supply, charge-sensitive amplifiers, and associated logic. The EUV channel also contains a solar occultation mechanism to allow solar flux to enter the telescope when the sun is still 20 degrees off-axis from the primary telescope. The far ultraviolet channel (FUV) will be used for imaging spectroscopy and spectroscopic measurements of the structure and composition of the atmospheres of Titan and Saturn and of the rings. The FUV is similar to the EUV channel except for the grating ruling density, optical coatings, and detector details. The FUV electronics are similar to those for the EUV except for the addition of a high-voltage power supply for the ion pump. The high-speed photometer channel (HSP) will perform stellar occultation measurements of the structure and density of material in the rings. The HSP resides in its own module and measures undispersed (zero-order) light from its own parabolic mirror with a photomultiplier tube detector. The electronics consist of a pulse-amplifier-discriminator and a fixed-level high-voltage power supply. The hydrogen-deuterium absorption cell channel (HDAC) will be used to measure hydrogen and deuterium in the Saturn system using a hydrogen cell, a deuterium cell, and a channel electron multiplier (CEM) detector to record photons not absorbed in the cells. The hydrogen and deuterium cells are resonance absorption cells filled with pure molecular hydrogen and deuterium, respectively. They are located between an objective lens and a detector. Both cells are made of stainless steel coated with teflon and are sealed at each end with MgF2 windows. The electronics consist of a pulse-amplifier- discriminator, a fixed-level high-voltage power supply, and two filament current controllers. The UVIS microprocessor electronics and control subassembly consists of input-output elements, power conditioning, science data and housekeeping data collection electronics, and microprocessor control elements. " Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Voyager 2 Radio Science investigations at Neptune utilized instrumentation with elements both on the spacecraft and at the DSN. Much of this was shared equipment, being used for routine telecommunications as well as for Radio Science. The performance and calibration of both the spacecraft and tracking stations directly affected the radio science data accuracy, and they played a major role in determining the quality of the results. The spacecraft part of the radio science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Specifications - Spacecraft ====================================== The Voyager 2 spacecraft telecommunications subsystem served as part of a radio science subsystem for investigations of Neptune. Many details of the subsystem are unknown; its 'build date' is taken to be 1977-08-20, which was the launch date for Voyager 2. Instrument Id : RSS Instrument Host Id : VG2 Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : 1977-08-20 Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK Instrument Overview - Spacecraft ================================ The spacecraft radio system was constructed around a redundant pair of transponders. Each transponder was equipped with an S-band receiver (2115 MHz nominal frequency) and transmitters at both S-band (2295 MHz nominal) and X-band (8415 MHz nominal). Compared with S-band, X-band is less sensitive to plasma effects by a factor of about 10; use of both frequencies coherently on the 'downlink' allowed estimation of plasma content along the radio path. Use of X-band also significantly improved the quality of radio tracking data for gravity investigations. The transponder generated downlink signals in either 'coherent' or 'non-coherent' modes, also known as 'two-way' and 'one-way,' respectively. When operating in the coherent mode, the transmitted carrier frequency was derived coherently from the received uplink carrier frequency with a 'turn-around ratio' of 240/221 at S-band and (11/3)*240/221 at X-band. In non-coherent mode the transmitted frequency was controlled by an on-board oscillator; the X- and S-band remained coherent in the ratio 11/3. A single Ultra-Stable Oscillator (USO) was used during radio occultations; it provided stabilities several orders of magnitude better than the conventional crystal oscillators, which were part of each transponder. Stability of the Voyager 2 USO was specified in terms of its Allan Deviation -- the fractional frequency deviation from linear drift [ALLAN1966]. Over 10 minute periods, the Allan Deviation ranged from 10^-12 to 4 10^-12 for integrations of 1-10 sec. Long-term fractional drift of the oscillator was about 5 10^-11 per day. Although the oscillator was hardened, there were discontinuities in the drift when the spacecraft passed through the radiation belts of the outer planets. The equivalent microwave frequency of the USO at Voyager 2 Jupiter occultation ingress was 2,296,481,070.940 Hz (S-band) 8,420,430,593.447 Hz (X-band) Traveling wave tube or solid state amplifiers boosted the transponder output. Output powers of 9 and 26 watts could be selected at S-band; the choices at X-band were 12 and 22 watts. The signals were radiated via a 3.66 m diameter parabolic high gain antenna (HGA). The HGA transmit boresight gain of the HGA was 36 dB at S-band and 47 dB at X-band. The half-power half-width of the antenna beam was 0.32 degrees at X-band and 1.1 degrees at S-band. Transmit polarization was right-hand circular at S-band and either right- or left-hand circular at X-band. A Low-Gain Antenna (LGA) was mounted on the feed structure of the HGA and radiated approximately uniformly over the hemisphere into which the HGA pointed. It was used during maneuvers, spacecraft anomalies, and at other times when the HGA was not appropriate. For receiving, the S-band HGA gain was 35 dB at 2115 MHz and the polarization was right-hand circular. The receiving system noise temperature was approximately 2000K, the carrier tracking loop bandwidth was 18 Hz, and the ranging channel noise bandwidth was 1.5 MHz. More information can be found in [ESHLEMANETAL1977]. Science Objectives ================== Science objectives fell into two broad areas of investigation -- those that could be met using high-precision radiometric data (sometimes known as 'tracking' data) and those that could be met from studying characteristics of the radio signal after its interaction with an atmosphere, plasma, ring particles, or other intervening medium. The tracking data were fundamental to inferring the gravitational forces on the spacecraft and relativistic effects along the radio path; both the measured time delay during a two-way transmission and the Doppler shift were used. Investigators seeking knowledge of atmospheric structure, spatial and size distributions of ring particles, and velocity of the solar wind measured amplitude, frequency (and phase), and polarization of the radio signals which were captured by Earth receiving systems. There are, of course, investigations which use both types of data. Gravity Measurements -------------------- The frequency of the downlink carrier signal was precisely measured to determine the magnitude of the Doppler shift caused by acceleration of the spacecraft as it passed near either a single body or a system of bodies. Since the magnitude of the Doppler shift is related to the gravitational field strength, the mass of the body (or bodies) can be determined. If the radius of the body is known (as from calibrated images), the density can be calculated. Doppler and range tracking measurements yield accurate spacecraft trajectory solutions. Simultaneously with reconstruction of the spacecraft orbit, observation equations for the central mass, low order coefficients for the field, and a small number of ancillary parameters can be solved. Measurements of the gravity field provide significant constraints on inferences about the interior structure of target bodies. The Pioneer 10 and 11 spacecraft came closer to Jupiter than Voyager, so there was no net improvement in the Jupiter mass estimate from Voyager. But Voyager probed the Galilean satellites at closer range, and better mass estimates were obtained. The Voyager encounters with Saturn, in conjunction with the close flyby of Pioneer 11, yielded a mass estimate comparable to that of Jupiter along with several low-order zonal harmonic coefficients. Voyager 2 was targeted for a close encounter with Miranda, an inner satellite of Uranus; that, combined with long tracking arcs through the Uranian system, yielded the first good estimates of masses for the five largest satellites and an improved mass estimate for Uranus itself. The Voyager 2 very close near-polar flyby with Neptune yielded estimates for the zonal harmonic coefficients J2 and J4 in addition to estimates for the mass of both Neptune and Triton. Atmospheric and Ionospheric Radio Occultation Measurements -------------------------------------------------- Atmospheric measurements by the method of radio occultation contribute to an improved understanding of structure, circulation, dynamics, and transport in atmospheres of remote planetary bodies. These results are based on detailed analysis of the radio signal received from the spacecraft as it enters and exits occultation by the planet. Three phases of an atmospheric investigation may be defined. The first is to obtain vertical profiles of atmospheric structure (temperature and pressure in the neutral atmosphere and electron density in the ionosphere) with emphasis on large- scale phenomena. During this stage, it is necessary to know the mean molecular weight of the atmosphere; for Voyager the hydrogen-helium mixing ratio could be determined for each planet using the radio data in conjunction with Voyager IRIS data. Second is to investigate absorption at various levels in the atmosphere -- such as by methane. Third is to study details of the structure, such as result from propagation of buoyancy waves within a neutral atmosphere or from alignment of charged particles along magnetic field lines in an ionosphere. Retrieval of atmospheric profiles requires coherent samples of the radio signal that has propagated through the atmosphere, plus accurate knowledge of the antenna pointing and the spacecraft trajectory. The spatial and temporal coverage in radio occultation experiments are determined by the observing geometry, including the spacecraft trajectory. For deep atmospheres, changes in antenna pointing may be required to compensate for refractive bending by the atmosphere. At Jupiter and Saturn both diametric and grazing occultations were obtained using the two Voyager spacecraft; measurements were obtained at both equatorial and polar latitudes. Voyager 1 also obtained profiles for Titan. Voyager 2 continued to Uranus and Neptune, and also obtained occultation profiles at Triton. Radio Measurements on Planetary Rings Instrument Overview =================== The Voyager 2 Radio Science investigations at Neptune utilized instrumentation with elements both on the spacecraft and at the DSN. Much of this was shared equipment, being used for routine telecommunications as well as for Radio Science. The performance and calibration of both the spacecraft and tracking stations directly affected the radio science data accuracy, and they played a major role in determining the quality of the results. The spacecraft part of the radio science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Specifications - Spacecraft ====================================== The Voyager 2 spacecraft telecommunications subsystem served as part of a radio science subsystem for investigations of Neptune. Many details of the subsystem are unknown; its 'build date' is taken to be 1977-08-20, which was the launch date for Voyager 2. Instrument Id : RSS Instrument Host Id : VG2 Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : 1977-08-20 Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK Instrument Overview - Spacecraft ================================ The spacecraft radio system was constructed around a redundant pair of transponders. Each transponder was equipped with an S-band receiver (2115 MHz nominal frequency) and transmitters at both S-band (2295 MHz nominal) and X-band (8415 MHz nominal). Compared with S-band, X-band is less sensitive to plasma effects by a factor of about 10; use of both frequencies coherently on the 'downlink' allowed estimation of plasma content along the radio path. Use of X-band also significantly improved the quality of radio tracking data for gravity investigations. The transponder generated downlink signals in either 'coherent' or 'non-coherent' modes, also known as 'two-way' and 'one-way,' respectively. When operating in the coherent mode, the transmitted carrier frequency was derived coherently from the received uplink carrier frequency with a 'turn-around ratio' of 240/221 at S-band and (11/3)*240/221 at X-band. In non-coherent mode the transmitted frequency was controlled by an on-board oscillator; the X- and S-band remained coherent in the ratio 11/3. A single Ultra-Stable Oscillator (USO) was used during radio occultations; it provided stabilities several orders of magnitude better than the conventional crystal oscillators, which were part of each transponder. Stability of the Voyager 2 USO was specified in terms of its Allan Deviation -- the fractional frequency deviation from linear drift [ALLAN1966]. Over 10 minute periods, the Allan Deviation ranged from 10^-12 to 4 10^-12 for integrations of 1-10 sec. Long-term fractional drift of the oscillator was about 5 10^-11 per day. Although the oscillator was hardened, there were discontinuities in the drift when the spacecraft passed through the radiation belts of the outer planets. The equivalent microwave frequency of the USO at Voyager 2 Jupiter occultation ingress was 2,296,481,070.940 Hz (S-band) 8,420,430,593.447 Hz (X-band) Traveling wave tube or solid state amplifiers boosted the transponder output. Output powers of 9 and 26 watts could be selected at S-band; the choices at X-band were 12 and 22 watts. The signals were radiated via a 3.66 m diameter parabolic high gain antenna (HGA). The HGA transmit boresight gain of the HGA was 36 dB at S-band and 47 dB at X-band. The half-power half-width of the antenna beam was 0.32 degrees at X-band and 1.1 degrees at S-band. Transmit polarization was right-hand circular at S-band and either right- or left-hand circular at X-band. A Low-Gain Antenna (LGA) was mounted on the feed structure of the HGA and radiated approximately uniformly over the hemisphere into which the HGA pointed. It was used during maneuvers, spacecraft anomalies, and at other times when the HGA was not appropriate. For receiving, the S-band HGA gain was 35 dB at 2115 MHz and the polarization was right-hand circular. The receiving system noise temperature was approximately 2000K, the carrier tracking loop bandwidth was 18 Hz, and the ranging channel noise bandwidth was 1.5 MHz. More information can be found in [ESHLEMANETAL1977]. Science Objectives ================== Science objectives fell into two broad areas of investigation -- those that could be met using high-precision radiometric data (sometimes known as 'tracking' data) and those that could be met from studying characteristics of the radio signal after its interaction with an atmosphere, plasma, ring particles, or other intervening medium. The tracking data were fundamental to inferring the gravitational forces on the spacecraft and relativistic effects along the radio path; both the measured time delay during a two-way transmission and the Doppler shift were used. Investigators seeking knowledge of atmospheric structure, spatial and size distributions of ring particles, and velocity of the solar wind measured amplitude, frequency (and phase), and polarization of the radio signals which were captured by Earth receiving systems. There are, of course, investigations which use both types of data. Gravity Measurements -------------------- The frequency of the downlink carrier signal was precisely measured to determine the magnitude of the Doppler shift caused by acceleration of the spacecraft as it passed near either a single body or a system of bodies. Since the magnitude of the Doppler shift is related to the gravitational field strength, the mass of the body (or bodies) can be determined. If the radius of the body is known (as from calibrated images), the density can be calculated. Doppler and range tracking measurements yield accurate spacecraft trajectory solutions. Simultaneously with reconstruction of the spacecraft orbit, observation equations for the central mass, low order coefficients for the field, and a small number of ancillary parameters can be solved. Measurements of the gravity field provide significant constraints on inferences about the interior structure of target bodies. The Pioneer 10 and 11 spacecraft came closer to Jupiter than Voyager, so there was no net improvement in the Jupiter mass estimate from Voyager. But Voyager probed the Galilean satellites at closer range, and better mass estimates were obtained. The Voyager encounters with Saturn, in conjunction with the close flyby of Pioneer 11, yielded a mass estimate comparable to that of Jupiter along with several low-order zonal harmonic coefficients. Voyager 2 was targeted for a close encounter with Miranda, an inner satellite of Uranus; that, combined with long tracking arcs through the Uranian system, yielded the first good estimates of masses for the five largest satellites and an improved mass estimate for Uranus itself. The Voyager 2 very close near-polar flyby with Neptune yielded estimates for the zonal harmonic coefficients J2 and J4 in addition to estimates for the mass of both Neptune and Triton. Atmospheric and Ionospheric Radio Occultation Measurements -------------------------------------------------- Atmospheric measurements by the method of radio occultation contribute to an improved understanding of structure, circulation, dynamics, and transport in atmospheres of remote planetary bodies. These results are based on detailed analysis of the radio signal received from the spacecraft as it enters and exits occultation by the planet. Three phases of an atmospheric investigation may be defined. The first is to obtain vertical profiles of atmospheric structure (temperature and pressure in the neutral atmosphere and electron density in the ionosphere) with emphasis on large- scale phenomena. During this stage, it is necessary to know the mean molecular weight of the atmosphere; for Voyager the hydrogen-helium mixing ratio could be determined for each planet using the radio data in conjunction with Voyager IRIS data. Second is to investigate absorption at various levels in the atmosphere -- such as by methane. Third is to study details of the structure, such as result from propagation of buoyancy waves within a neutral atmosphere or from alignment of charged particles along magnetic field lines in an ionosphere. Retrieval of atmospheric profiles requires coherent samples of the radio signal that has propagated through the atmosphere, plus accurate knowledge of the antenna pointing and the spacecraft trajectory. The spatial and temporal coverage in radio occultation experiments are determined by the observing geometry, including the spacecraft trajectory. For deep atmospheres, changes in antenna pointing may be required to compensate for refractive bending by the atmosphere. At Jupiter and Saturn both diametric and grazing occultations were obtained using the two Voyager spacecraft; measurements were obtained at both equatorial and polar latitudes. Voyager 1 also obtained profiles for Titan. Voyager 2 continued to Uranus and Neptune, and also obtained occultation profiles at Triton. Radio Measurements on Planetary Rings Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem Instrument Overview =================== The Radio Science investigations on Cassini were unique in that they utilized instrumentation with elements both on the spacecraft and on the ground. The spacecraft element was further distinguished in being distributed among several subsystems on the Cassini Orbiter. Cassini Radio Science can be regarded as a solar-system-sized instrument observing at microwave frequencies, with one end of the radio path on the spacecraft and the other end at the NASA Deep Space Network (DSN) stations on the ground. The Radio Science 'instrument' operated in two fundamental modes, depending on whether the microwave optical path had one or two legs. For 'two-way' measurements, the 'uplink' signal from the ground could be a single carrier at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be transmitted at the same time. The spacecraft radio equipment then acted as a repeater, collecting the carrier signal with the spacecraft High Gain Antenna (HGA), transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, or 32 GHz), amplifying and re-collimating it, and sending it back to Earth. The returned signal was detected using DSN ground receiving equipment, amplified and downconverted, and recorded for later analysis. Uplink signals were generated by the DSN exciter, using the local frequency and timing system as a reference. At Launch and Cruise, this reference was a Hydrogen Maser. Note: in the future, these masers could be combined with a Compensated Sapphire Oscillator (CSO) to meet Radio Science requirements for increased stability. The uplink signals were amplified, radiated through feed horns, and collimated by a large parabolic ground antenna, which was continuously aimed at the Cassini spacecraft. The actual transmission frequencies could be adjusted to allow the spacecraft receivers to lock to the uplink signals and to compensate, in finite steps, for the main part of the Doppler effect between the Earth and the Cassini Orbiter. For one-way measurements, the signal source was on board the Cassini Orbiter. The output from an extremely stable on-board reference oscillator (the Ultrastable Oscillator, or USO) was transformed to downlinks at S-band (2.3 GHz), X-band (8.4 GHz), or Ka-band (32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency Instrument Subsystem (RFIS). These signals were amplified and radiated through the HGA toward Earth. After passing through the medium of interest (plasma, rings, a neutral atmosphere, or gravitationally curved space), the perturbed signal was collected by a DSN antenna, amplified and downconverted, and recorded for later analysis. The spacecraft part of the Cassini Radio Science instrument is described immediately below; that is followed by a description of the DSN (ground) part of the instrument. Instrument Overview - Spacecraft ================================ On the Cassini Orbiter, the Radio Science instrument was encompassed in the Radio Science Subsystem (RSS). RSS was really a virtual subsystem comprising elements from three physical spacecraft subsystems, two of which had other functions to perform. The subsystems that participated in RSS were the RFIS, the RFS, and the Antenna Subsystem. Specifications included: Instrument Id : RSS Instrument Host Id : CAS Pi Pds User Id : UNK Instrument Name : RADIO SCIENCE SUBSYSTEM Instrument Type : RADIO SCIENCE Build Date : UNK Instrument Mass : UNK Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Manufacturer Name : UNK ----- F2 -------- F2 ----- | |<----------------------------------| | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- |--->| TWTA |--->| |--->| | | DST | F3 | BAND | BAND | F7 ------ F7 ----- F7 | | | | |EXCITER| HYBRID | | | | | | | | F7 ---------- F8 | HGA | | | | | |<----| Ka-BAND |<---------| | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | ----- ------------- ----- | | | USO | ----- ----- (a) ----- -------- ----- | | | | | HGA | | | ---------------- | X-BAND | | LGA1| | | F3 | X-BAND | X-BAND| F3 |DIPLEXER| F3 | LGA2| | |--------->| HYBRID | TWTA |------>| |--------->| | | | ---------------- -------- ----- | | F4 ---------------- F5 ------ F5 ----- F5 ----- | |--------->| | |--->| Ka- |--->| |--->| | | | | | | | BAND | | BPF | | | | |--------->| Ka- | Ka- | | TWTA | | | | | | DST | F3 | BAND | BAND | ------ ----- | | | | |EXCITER| HYBRID | | | | | | | | ---------- | HGA | | | | | | | Ka-BAND | | | | | ---------------- |TRANSLATOR| | | | | F4 ------------- ---------- F6 | | | |-------------->| S-BAND |------------- | | | TRANSMITTER | | | | | F4 ----- ------------- ----- | |<----| USO | ----- ----- (b) Fig. 1: Configuration of the Cassini Orbiter Radio Science Subsystem for (a) two-way operation and (b) one-way operation. The RFS comprised the USO, DST, X-Band TWTA, and X-Band Diplexer. The RFIS comprised the Ka-Band Exciter, Hybrid, Ka-Band TWTA, BPF (Band Pass Filter), Ka-Band Translator, and S-Band Transmitter. The Antenna comprised the HGA, LGA1, and LGA2. In (a) F1 is the DST receiver channel frequency and Fk is the KAT VCO frequency; in (b) F1 is the DST exciter channel frequency. Then the other frequencies are as follows: F2 = 749*F1 (~7.2 GHz; X-band up) F3 = 880*F1 (~8.4 GHz; X-band down) F4 = 12*F1 (~115 MHz; internal reference) F5 = 3344*F1 (~32 GHz; Ka-band down) F6 = 240*F1 (~2.3 GHz; S-band down) F7 = 294*Fk (~32 GHz; Ka-band down) F8 = 315*Fk (~34 GHz; Ka-band up) Radio Frequency Subsystem |
