“Why do we need space segment in satellite?”. “Is it mandatory to have space segment in satellite?” .Space segment include the satellites and it also includes ground facilities needed to keep the satellites operational, by Tracking, Telemetry and Command (TT&C) facilities. The space segment has the Payload refers to the equipment used to provide the service for which the satellite has been launched. It has power supply, attitude control, Thermal control, Transponder and antennas. The primary electrical power for operating the electronic equipment is obtained by solar cells. The attitude of the satellite refers to its orientation in space. Attitude control is necessary and it can be spin stabilization or momentum wheel stabilization. The Thermal Control helps to maintain the temperature of satellite to an optimum level to avoid the satellite from damaging due to the nature of earth’s albedo. The Uplink and Downlink frequency are usually kept different in order to avoid interferences between the two signals. The transponder is the series of interconnected units which forms the single communication channel between the receiving and transmitting antennas in communication satellite. It has Band pass filter for receiving desired frequency of signals, Wide band receiver which converts the received frequency to a lower downlink frequency and then amplifies it with Power amplifier. The space segment has receiving and transmitting antenna for reception and transmission of uplink and downlink frequencies respectively from the earth segment.