HOW DO 'SATELLITES' WORK?

Satellites help us navigate, communicate, monitor the environment, and forecast weather. A satellite is basically a self-contained communications system that can receive signals from Earth. Signals are sent from earth with the help of an antenna on the ground, which is called Earth Station. The high-powered, high frequency signals sent to the satellite are known as uplinks. The satellite receives uplinks and retransmits them back to Earth. These are called downlinks. Satellites receive and transmit signals with the help of a transponder, which is basically an integrated receiver and transmitter of radio signals.

  

In most cases, as in the case of communication satellites, once the signals are received by the Earth Station, they are distributed. For example, programmes on television are routed through satellites. Let's assume yo are watching a show made in Hollywood studio. To get the signal to you, the studio will broadcast it to the satellite through an uplink. The satellite will then rebroadcast the signal down to your local station, which is sent to your TV through a downlink. Since satellites fly in the sky and are above the clouds and atmosphere, they have a clear view of large areas of Earth. So they can collect more data than any other instrument on the ground. Before satellites were invented, TV signals were used. However, these didn't work too well- the signals only travelled in straight lines, which were often interrupted by mountains or tall buildings. Moreover, they were unable to follow the Earth's curve.