UHF transceiver, Ku transmitter
The communication subsystem (COM) provides communications between the satellite and the groundstation. There are two different radio systems in the satellite. The first operates on the UHF waveband and is used for transmitting satellite communications (remote control) and satellite monitoring (telemetry). The second radio is operating in the 10 GHz band and is used to download satellite images. Without a communication subsystem, the satellite would be completely "on its own", there would be no way to control the satellite and transmit data stored on it to Earth.
In addition to radio waves, the radio transmitter allocates a significant amount of heat. Under good conditions, the generated heat dissipates in ambient air, but this cooling mode can not be used in space vacuum. Therefore, the generated heat must be directed to the body of the satellite, from which the latter, in its turn, releases the space from the thermal radiation.