Page 36 - SATELLITE AND RADAR COMMUNICATION SYSTEM

a. Power supply
The satellite present in an orbit should be operated continuously during its life
span. So, the satellite requires internal power in order to operate various electronic
systems and communications payload that are present in it.

b. Propulsion

Propulsion subsystem is used to provide the thrusts required to impart the
necessary velocity changes and transfer orbit of the satellite, such as those required
for station keeping.

c. Altitude and Orbit Control
Altitude and Orbit Control (AOC) subsystem consists of rocket motors, which are
capable of placing the satellite into the right orbit, whenever it is deviated from the
respective orbit. AOC subsystem is helpful in order to make the antennas, which are

of narrow beam type points towards earth.

d. Thermal Control

Thermal control subsystem is essential to maintain the satellite platform within its
operating temperature limits for the type of equipment on board the satellite.

e. Telemetry, Tracking and Command
Telemetry, Tracking, Command to monitors the on-board equipment operations,
transmits equipment operation data to the earth control station, and receives the

earth control station's commands to perform equipment operation adjustments.

f. Antenna
Antennas are present in both satellite and earth station. Satellite antennas
perform two types of functions. Those are receiving of signals, which are coming
from earth station and transmitting signals to one or more earth stations based on
the requirement. In other words, the satellite antennas receive uplink signals and
transmit downlink signals.

g. Transponder
The subsystem, which provides the connecting link between transmitting and
receiving antennas of a satellite is known as Transponder. It is one of the most
important subsystem of space segment subsystems.
Transponder performs the functions of both transmitter and receiver (Responder)
in a satellite. Hence, the word ‘Transponder’ is obtained by the combining few
letters of two words, Transmitter (Trans) and Responder (ponder).

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Satellite System Elements