The CONTOUR radio communications system

This paper provides a detailed description of the radio communications system developed for the Comet Nucleus Tour (CONTOUR) Project. The communications system embodies a delicate balance of minimizing cost while providing the high performance needed to support a deep-space science mission. CONTOUR employs a transceiver-based X-band system instead of traditional deep-space transponders. For navigation, we have a conventional ranging channel and employ a novel Doppler frequency measurement technique. A reference oscillator with low phase noise is included to allow narrow bandwidth downlink carrier tracking at the ground stations. The antenna system is a combination of high- and low-gain antennas to support high-data-rate science returns and low-data-rate emergency operations. As CONTOUR is spin stabilized for most of the mission, including emergency operations, all antennas have been designed to provide continuous coverage around 360/spl deg/ of spacecraft rotation.