WHAT IS THE SATELLITES? AND SATELLITES UPLINK AND DOWNLINK SPEED ?

Communication Satellite


INTRODUCTION




  • The real beginning in the field of satellite communication was made in 1957, as a first man made satellite went into the ordit.
  • the process of sending information around the world has been revolutionized by the advent of satellites.C

COMMUNICATIONSATELLITES



    • A communication satellite is basically a microwave link repeater. it receives the energy beamed up from an earth station, amplifiers and returns it to the earth at a frequency of a couple of GHz away to prevent interference between the uplink and downlink.
    • A satellite 35800 km from the earth will complete a revolution in 24 hours.
    • Early bird was the first satellite which was launched by USA in august , 1965.
    • If the direction of the satellite's revolution is the same as the earth rotation then the orbit is said to a posigrade orbit.
    • when the satellite is in an elliptical orbit , the highest point from the earth of that orbit is called the Apogee.
    • In an elliptical orbit, the lowest point of that orbit from the earth is called Perigee.
    • Types of communication satellite.

    The communication satellite can be of two basic types

    1. Passive satellite


    A passive satellite acts merely as a reflector of signals. These satellite need very powerful ground systems. These satellite do not have electronic parts which may fail and render the satellite useless. 
          Passive satellite can be of two types.
    • discrete structure satellite;or 
    • where a large volume of space is filled with a large number of tiny passive satellite ( dipoles).

    2. Active satellite


    An active satellite receives the signal , amplifier it and transmits it back to other points on the earth.
     Satellite spacecraft systems

    A complete satellite consists of several subsystem, but most important of these are ;

    1. Power supply system 


    • solar array 
    • battery
    • power supply control circuit.

    2. Altitude and orbit control

    • sensor.
    •  altitude control.
    •  orbit control.
    • propulsion system
    • antenna control

    3. Telemetry and telecontrol


    4. Communication



     .uplink and downlink 

    Satellite uplink speed 6GHz .
    Satellite downlink speed 4GHz.

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