An artificial satellite is a man-made Moon that orbits around the Earth. With the help of rockets, they are launched into geostationary orbits. 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 the earth station. This is how a signal travels thousands of kilometers.
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 the 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.
