NASA - National Aeronautics and Space Administration
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



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



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. "




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 allo