Telemetry, Tracking and Command Systems of Spacecraft

摘要

The Telemetry, Tracking and Command (TT&C) Systems of a spacecraft provides the most vital telecommunication link between a satellite and ground station. The TT&C systems provide the uplink for command, downlink for monitoring the various health parameters through telemetry and much needed tracking information for the satellite for monitoring its position in orbit. The link is provided using a ground station and onboard telecommand&tracking data receiving systems, onboard decoder and telemetry transmitter. The TT&C link of a satellite is of prime importance, right from the time of its launch to the end of the mission. The uplink and downlink frequencies could be in VHF/S/X/Ku or Ka bands depending on the mission requirements, system development status and facilities available. The development, testing and fabrication of these systems are quite involved, tricky and difficult. It requires a lot of expertise to develop them. A brief description and specifications mainly related to their developments in ISRO have been presented in this paper.