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 .