The Cassini Radio Science instrument included elements on both the spacecraft
             and the ground. The spacecraft element (covered by this context product) was 
             further distributed among several subsystems on the Orbiter, while the ground 
             element included NASA Deep Space Network (DSN) complexes in California, 
             Australia, and Spain and occasional support from other ground stations such 
             as antennas of the European Space Agency tracking network.
 
             The Radio Science 'instrument' operated in two fundamental modes. For 'two-way' 
             measurements, the 'uplink' signal from the ground could be a single carrier 
             at either X-band (7.2 GHz) or Ka-band (34 GHz); or both carriers could be 
             transmitted at the same time.  The spacecraft radio equipment then acted as a
             repeater, collecting the carrier signal with the spacecraft High Gain Antenna 
             (HGA) and transforming it to one or more 'downlink' frequencies (2.3 GHz, 8.4 GHz, 
             or 32 GHz) by elements in the Radio Frequency Subsystem (RFS) and Radio Frequency
             Instrument Subsystem (RFIS). For 'one-way' measurements, the signal source was 
             on board the Cassini Orbiter; the output from an Ultrastable Oscillator (USO) was 
             transformed to downlinks at 2.3, 8.4, or 32 GHz.   
             
             The downlink signals were amplified and radiated through the HGA toward Earth.
             After passing through the medium of interest (e.g., plasma, rings, a neutral 
             atmosphere or gravitationally curved space), the perturbed signal was collected  
             by a ground antenna, amplified, down-converted, and recorded for later analysis.