What are communication satellites?

          There was a time when man used to communicate by beating drums or burning fires. Those days, in the absence of any scientific knowledge, it was extremely difficult to send messages to distant places. Today, we have different means of communication like the telephone, radio, television and the press. Now scientists have added artificial communication satellites or comsats to send telephone, radio, telex, fax messages and television signals around the world.

          An artificial satellite is a man-made Moon that orbits around the Earth. With the help of rockets, they are launched into geostationary orbits. This means that they are placed in fixed orbits over the equator about 36,000 km high where they orbit the Earth in exactly 24 hours. Because of this they appear to remain stationary in the sky from the Earth. Artificial satellites are of many different shapes and sizes and are sent into orbit for several different reasons. They usually have solar cells which convert the energy of the Sun into electricity which is used to run the satellite instruments. 

          Communication satellites pick up the signals transmitted from a point on the Earth and relay them to the other side of the world by amplifying them and then beaming them down to a ground station. Communication satellites have different channels for telephone, radio and television signals. The signal is first sent to the satellite with the help of high-frequency microwaves. This is received by the antenna fitted in the satellite. After amplifying, it is transmitted by a transmitter. Its power is increased by a transponder. The signal is received by the earth station. This is how a signal travels thousands of kilometres. If a message is sent through conventional methods, very long cables are required. Today, telephone messages between several countries are exchanged through satellites.


          The story of communications began in 1945 when some microwave signals were sent to the Moon. They got reflected from its surface and were received on the Earth. Subsequently Echo I and II were launched by the United States in 1960. However, their signals received on the Earth were very weak. In 1962, Telstar became the first communication satellite to send live television pictures across the Atlantic Ocean. Its one revolution round the earth took 158 minutes. The ground stations had to track it and its services were sometimes interrupted.

          With the launching of the Syncom III in 1964, these hurdles were overcome. It was a geostationary satellite. After this Intelsat (International Telecommunication Satellite Organization) programme came into existence. So far, five satellites have been launched under this scheme. Intelsat I had 480 telephone channels and one T.V. channel. This number was increased to 30,000 telephone channels and 12 coloured T.V. channels in Intelsat V.

          Upto 1981, there were only five countries – USA, USSR, Canada, Indonesia and Japan – who had launched their satellites. On 10 April, 1982, India also launched its first communication satellite INSAT-1A and joined this exclusive club.

          During the last 20 years rapid strides have been made in the field of communication satellites with provisions for thousands of television channels and millions of telephone channels. Now the new communication satellites like Apstar and ASIANET provide a satellite T.V. network to the whole world and Asia respectively. The communication satellites are making the world smaller day by day.