From Aff to Ccnt: Jpl’s Evolving Family of Multi- Function Constellation Transceivers

I . ABSTRACT JPL is developing novel RF tracking sensors for both of NASA’s New Millennium Program constellation missions, ST-3LStarLight and ST-5. ST-3/StarLight9 the Separated Spacecraft Inlerferometer, is a two-satellite formation in heliocentric orbit designed to demonstrate various technologies required for space interferometry. Scheduled for a 2006 launch. ST-3 will fly JPL’s Autonomous Formation Flying (AFF) sensor for sub-cm inter-spacecraft ranging accuracy and 1 arcmin bearing accuracy. ST-5, the Nanosatellite Constellation Trailblazer, is a three-satellite consteIlation in geosynchronous transfer orbit designed to test and validate technologies in advance of MagCon, the large magnetospheric constellation scheduled to enter engineering development in 2006. Scheduled for launch in late 2003, each of the ST-5 spacecraft will carry JPL’s Constellation Communications and Navigation Transceiver (CCNT), integrating interspacecraft ranging, communications, and GPS -based absolute positioning. This paper describes the profiles and requirements of the ST-3 and ST-5 missions: and discusses the unique technological challenges each of them presents. Both the AFF and CCNT trace their heritage to GPS receivers, using measurements of both RF carrier phase and a ranging code. They will operate, however, at very different frequency bands: the AFF at Ka-band, and the CCNT at S-band.