TT&C
TT&C is the English abbreviation for Telemetry, Tracking, and Command , sometimes also Telemetry, Tracking, and Control or Telemetry, Telecontrol, and Ranging ( TT&R ), in German about satellite control and path tracking .
The term summarizes the operations that a ground station must carry out to control and operate a satellite :
- the telemetry received process measurement data of the satellite, such as height, electric voltages of the batteries and solar cells, temperature or position in space. This gives the ground station a picture of the operational readiness of the satellite and its payload .
- Tracking includes trajectory tracking and prediction.
- Under Command refers to all control commands sent from the ground station to the satellite. This includes the commands for using the engines, commands for aligning the satellite, solar panels or antennas, as well as commands for controlling the payload. While in earlier times many of these control functions were performed by the ground station, satellites increasingly have their own autonomous intelligent systems that perform most of these functions automatically. They have their own threshold values and error monitoring procedures so that fewer and fewer of these tasks need to be influenced from the ground. Intervention from the ground station is then only necessary if the on-board control systems are no longer sufficient.