Deep Space Receiver for Cassini-Huygens Radio Link

The CASSLNI-HUYGENS mission is a deep space mission for the exploration and the study of the atmosphere of Titan. The combined Orbiter-Probe spacecraft will reach the Saturn system about 8.5 years after the launch. At that time the Probe will be separated and its mission will start transmitting scientific and housekeeping data during the descent phase to the surface of Titan via S-band radio relay link. The Probe Data Relay Link is composed by the Probe Transmitter Terminal (PTT), on Huygens spacecraft, and the Orbiter Receiving Terminal (ORT), on Cassini spacecraft. The PTT includes two chains which tranrsmit the phase modulated carriers at two different frequencies with opposite circular polarizations. On the orbiter the two signals are discriminated and separately amplified by the LNAs. The receivers acquire and synchronize the carter and subcarrier and provide the data demodulation and decoding. Major requirements of the deep space receivers are fast signal acquisition and demodulation capability at very low C/No. The paper describes the Orbiter Receiver architecture underlying the advantages of a fully digital approach.