A communication satellite is a space craft, provided with microwave receiver and transmitter. It is placed in an orbit around the earth. The India remote sensing satellites are
IRS-IA, IRS-IB and IRS-IC
The line-of-sight microwave communication through satellite is possible if the communication satellite is always at a fixed location with respect to the earth, e. g., the satellite which is acting as a repeater must be at rest with respect to the earth. It is so far a satellite known as geo-stationary satellite.
The basic requirements for geostationary satellites are as follows:
1. The time period of revolution of the satellite around the earth is equal to the time period of rotation of earth about its polar axis i. e., 24 h.
2. The sense of revolution of the satellite around the earth is the same as that of the earth about its polar axis i. e., from west to east.
3. The orbital plane of revolution of satellite is concentric and coplanar with the equatorial plane of earth.
4. The height of geostationary satellite above the equator of earth is nearly 36000 km and its orbital velocity is nearly 3.1 km / s.
The orbit in which the gee-satellite above revolves around the earth is known as geo-synchronous orbit. As its angular speed is synchronised with the angular speed of the earth. therefore, the geo-stationary satellite is also known as geo-synchronous satellite.
Merits of Satellites Communication
1. The satellite communication covers wide area for broadcasting a8 compared to other communication systems i. e. it has wide coverage range.
2. The satellite communication is also used effectively in mobile communication.
3. The satellite communication is found to be much economical as compared to other communication systems on earth. Infact. the cost involved in satellite communication is independent of the distance.