Satellite Communication

The first satellite was launched in 1957 and then the satellite communication opened up new area for communication.We know the limitations of terrestrial communications.The line of sight communication range was limited by curvature of earth,therefore long distance communication was required to  adopt some other solutions.The greatest advantage of satellite communication is that there is a direct line of sight communication down to the earth,also earth station can communicate to the satellite,the advantage of satellite communication has solved many problems in the field of communication.The long distance communication requires cables and repeaters.The satellite communication does not require any cables or repeaters stations.With the satellite it is possible to cover a specific limited area for transmission.This area is called footprint area or satellite coverage area.This area can be as small as few square kilometers or as high as 40% of the total earth’s surface facing satellite,because of such complete coverage communication and information exchange between has been possible .Since the satellite and satellite communication has been quite above the earth’s surface,there is no electromagnetic interference generated on the earth.The attenuation due to all these factors are overcome.

Even though the manufacturing and launching of satellite is quite costly as compared to establishing a transmission station on earth,the satellite provides a lot of application.Since the satellite is launched quite above the earth in space,it receives solar energy from the sun over a 95% of the period.Therefore the power required to operate these satellites is obtained from solar energy which is then converted ti electrical energy.The satellite is provided  with large solar panels for satellite to energy conversions.The automatic control for solar panel is such that they always face the sun.Whenever the sunlight is not available then the internal battery provides the required for operation,since solar energy is used even the life of the satellite is quite larger.

The main function of satellite is to get information from the earth station and to retransmit the information to the given area.Thus in most of the application the satellite acts as the repeater station .It takes the information from one or more earth station on one frequency band.This received information is then filtered,amplified and then retransmitted to the required area on some other frequency band.Separate frequencies are used by the satellite for transmission and reception so that they are not mixed up with each other.Some satellites transmit the information from earth and they receive the control and operating signals from the earth workstations,such satellites are used for weather forecasting,survey,navigation,radar application,air traffic control and other similar applications.Cameras and antennas are installed on the earth’s surface such that it can take photographs of the earth and other objects.The national and international communications are established through INTERNATIONAL TELECOMMUNICATION SATELLITES (INTELSAT).