Telemetry, Tracking & Command (TT&C)

TT&C is the subsystem responsible for all communications between a satellite and its ground control. Telemetry transmits spacecraft health data (temperatures, voltages, attitude, battery state, error logs) to the ground. Tracking provides ranging data for orbit determination. Command allows operators to upload instructions, update software, perform manoeuvres, and configure payloads. TT&C typically uses separate frequency bands from the payload to ensure operators can always reach the satellite even during payload failures. Loss of TT&C renders a satellite uncontrollable — it becomes space debris.