A space craft that orbits the earth is subjected to a wide range of temperatures as the spacecraft is exposed to deep space or to solar or planetary flux. If a component encounters a temperature which is too high or too low, it could be damaged or its performance could be severely affected. So it is essential that the satellite and all of its components remain in acceptable temperature ranges at all times. This is achieved by the thermal control system attached to the satellite.

The thermal control subsystem can be composed both of passive and of active items and works in two ways: