SatelliteTelemetry,TrackingandControlSubsystems.pdf

Satellite Telemetry, Tracking and Control Subsystems Col John E. Keesee October 29, 2003 Massachusetts Institute of 1 Technology Overview ? The telemetry, tracking and control subsystem provides vital communication to and from the spacecraft ? TTC is the only way to observe and to control the spacecraft’s functions and condition from the ground October 29, 2003 Massachusetts Institute of 2 Technology Outline ? TTC functions and trades ? Command System functions – Encoding/Decoding – Messages – Interfaces ? Telemetry systems – Sensors and transducers – ADC – Formats – Concerns/Design principles October 29, 2003 Massachusetts Institute of 3 Technology TTC Functions ? Carrier tracking ? Command reception and detection ? Telemetry modulation and transmission ? Ranging ? Subsystem operations October 29, 2003 Massachusetts Institute of 4 Technology Carrier Tracking ? Two-way coherent communication – Transmitter phase-locks to the received frequency – Transmitted frequency is a specific ratio of the uplink frequency ? Easy to find and measure the frequency received on the ground ? Doppler shift provides range rate October 29, 2003 Massachusetts Institute of 5 Technology Ranging ? Uplink pseudo-random code is detected and retransmitted on the downlink ? Turnaround time provides range ? Ground antenna