Cassini RSS: Radio Science Subsystem

For the radio science instrument, the radio signals from Cassini were transmitted to the NASA Deep Space Network complexes in Australia, Spain and the U.S.




About RSS

The Radio Science Subsystem was used to probe the Saturn system at radio frequencies. Unlike the other science instruments onboard the Cassini spacecraft, the radio science experiment included not just components scattered around the spacecraft but the large, Earth-based radio antennae of the Deep Space Network that received the signals transmitted by RSS as well. RSS utilized Cassini's high-gain antenna to transmit signals to the ground at one of three radio frequencies and to receive signals produced by the DSN. Its primary functions were to observe occultations and probe the gravity fields of bodies in the Saturn system. Assembled at the Jet Propulsion Laboratory, RSS incorporated parts supplied by JPL, NASA's Lewis Research Center, the John Hopkins University Applied Physics Laboratory, Italy's Agenzia Spaziale Italiana and other subcontractors. Science objectives for RSS include:
  • determining the gravity fields of the larger bodies in the Saturn system, including Titan, the large, icy satellites and Saturn itself,
  • probing Saturn's rings at centimeter wavelengths using occultation experiments to constrain their structure and the physical properties,
  • characterizing the non-axisymmetric structures in Saturn's rings, such as the bending and density waves and equatorial and inclined ringlets within the system
  • and investigating the vertical profiles of the atmospheres and ionospheres of Saturn and Titan through occultation observations.
Cassini's radio science experiment probed the Saturn system by transmitting radio signals at three distinct wavelengths: S-band (2.3 GHz), X-band (8.4 GHz) and Ka-band (32 GHz). For much of the Cassini mission, RSS was capable of operating in one of two distinct modes. Two-way measurements involved the DSN stations generating a single uplink carrier signal at either X-band (~7.4 GHz) or Ka-band (~34 GHz), with the actual transmission frequencies being adjustable in order to compensate, for example, for the Doppler effect between the Earth and the Cassini orbiter. The high-gain antenna would receive this uplink signal, transforming it to one of three signals (2.3 GHz, 8.4 GHz or 32 GHz) coherent with the uplink signal and returning an amplified signal to Earth which was recorded at the DSN. A variant of this two-way mode, referred to as three-way mode, involved the downlink signal being recorded on Earth through a different DSN antenna than the one generating the uplink signal. The second mode available to RSS was called one-way mode, which utilized the instrument's ultrastable oscillator to generate S-band, X-band or Ka-band signals with exceptional short-term phase and frequency stability. However, with the loss of the USO in late 2011, RSS was restricted to using two-way (three-way) mode for the remainder of the mission.
The engineering details of the RSS instrument and the science objectives it was built to address are described in further detail in the Space Science Reviews paper by Kliore et al. (2004).

Finding RSS Data

Search-for and Filter Raw Data

The Event Calendar is one way to find data associated with particular events such as auroral observations.
See the Master Schedule for a time ordered listing of observations by all instruments. This may help find data based on particular events, although the OPUS tool linked above will be much simpler to use in most circumstances.

Browse Raw Data Products

Gravity Occultations Bistatic Other Experiments

Gravity

Occultations

Bistatic

Other experiments

Processed Data Products

Selecting Data Products

Analyzing RSS Data

Once data products have been selected and retrieved, users will need appropriate software to read, manipulate and display that data. Below are listed software packages that will enable users to make use of RSS data.
End-to-end diffraction reconstruction of a complete event can be done with this open source software