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Satellite Subsystems

The modern satellite is an extremely complicated piece ofequipment composed of more than a half-dozen major

subsystems and thousands of parts. There are 2 main systemsin satellite communication.

1.Communication Payload: Repeater and antenna systemProvide all communications relay and processing functions.

2.Spacecraft Bus: (Power, control, and structure of the

spacecraft vehicle). the vehicle that powers and protects thepayload through all phases of the mission and operation

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1.Propulsion subsystem

The propulsion system is only partly thecomponents that get the satellite into orbit.Other chemical or electrical motors are used

to move the satellite back into the correctorbit when either atmospheric drag,magnetic fields or the solar winds deflect thesatellite out of it's correct trajectory. These

motors boost it back to the correct altitude,speed the satellite up, slow it down, orchange the angle of the trajectory.

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2.Power subsysem

The Power Subsystem generates, stores,controls and distributes electrical power tothe other subsystems on board.Solar panels are used in combination with

batteries to provide a constant source ofelectrical power on the satellite. Thebatteries are used when the satellite is notin direct sunlight, and allows the satellite to

continue to function. LEO satellites havegreater need of batteries, while GEOsatellites have less, as they are exposed tothe sun longer.

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3.Communication subsystem

The communications subsystem usestransmitters, receivers or transponders

(transmitter and receiver in onecomponent). The communicationssubsystem handles all transmit and receivecommunications functions. If it is a

communications satellite, this will be aheavy portion of the satellite'sconstruction.

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4.Superstructure subsystem

The satellite must survive theviolent forces of the rocket rideinto space. The superstructure ofthe satellite not only supports it inspace, but reduces the shock and

vibration the internal componentsmight suffer during the launch.

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5.Thermal control subsystem.

The whole point of the thermal system isto regulate the temperature of thesatellite's components. Too hot or too

cold, or too great a swing in temperaturewill prematurely end the useful life of asatellite. This system dissipates the heataway from earth, out into space, so as

not to interfere with the satellite'soperation.

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6.Attitude and orbit controlsubsystem

The satellite must face the earth at all

times. The attitude and orbit controlsystem allows the satellite to remainpointed correctly. These are often verysmall motors compared to the

propulsion system.

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7.Tracking Telemetry and Command

subsystem

The satellite must inform the satelliteoperations center what it's current state is,

and where it is located in orbit. Often asimple 'beacon' system is used to allow theground station to track the satellite in orbit.Additional information is relayed to the

ground, such as the craft's operatingtemperature, state of it's programs andoperating system, as well as a host of otherinternal functions.

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10. ANTENNA SUBSYSTEM

Antenna subsystem is also an essential componentof satellite system. Basically four main type ofantennas are used: these are Monopoles and dipoles(wire antennas) which are mainly used in VERYHIGH FREQUENCY AND ULTRA HIGH FREQUENCY.

2.> Horn antennas are mainly used at microwavefrequencies. Horns are actually used as feeds forreflector. 3.> Array antennas are actually phasedarray antennas which are used on satellites to form

multiple beams from single aperture. 4> Reflectorantennas are commonly used for earth stationantennas and the most widely employed shape of itis the parabolic with a feed placed at its focus.

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There are also many other subsystemslike Navigation Subsystem thatgenerates information necessary fordetermination of the satellite position.

Processing subsystem, this control

the entire satellite operations.Data storage subsystem thissubsystem temporally stores the imagedata and housekeeping data of on board

subsystems.Etc

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THANK YOU. ANY QUESTIONS?!THANK YOU. ANY QUESTIONS?!