A satellite is a most sophisticated communication device, which works as a relay station orbit up above the earths crust. All satellites have receivers, converters and transmitters with all the accessories needed for wireless communication. A typical communication satellite has 12 to 24 on board transponders. A Transponder is nothing but a package consisting of receivers, converters and transmitters and the normal output is calculated between 5 to 10 watts. It has the potential to operate in L-Band, C Band or KU Band or in the microwave range. KA-bands (18 to 31 GHZ) can also be operated in some cases. Communication through Mobile satellite system cannot be operated. Geosynchronous Earth Orbit Satellite - GEO: It is a satellite which orbits the earth some 22000 plus miles up above the equator. It is having a fixed direction corresponding to Earth. It is finely synchronized with the rotational speed of Earth so much so it would appear as though it stands stationery at that spot all the time. Earth-satellite-Earth time is about 0.25 seconds. Normal Bands operate on 4 to 6 GHZ (C-Band) and 12 to 14 GHZ (KU-Band normal frequency is 10.9 to 17 GHZ). Signals that go beyond 3 GHZ are considered microwaves. Low Earth Orbit Satellite - LEO system. In this system a constellation consisting quite a large number of satellites put on a circular orbit above the earths surface at a constant altitude of a few hundred miles (as against 22000 plus miles in GEO). The entire constellation is systematically arranged in such a way that at least one satellite in on sight always. Every geographical area is covered by the orbiting satellites. Internet access though wireless is possible in this configuration. L. Band - 0.5 to 1.5 GHZ - is operated which means satellite phone handset to satellite in quite possible. Medium Earth Orbit Satellite: MEO It is not stationery from a fixed or definite point on earths orbit like a GEO. In fact it is between a GEO and LEO. You need access methodology to access the satellite or use a precise frequency band in order to track the satellite with the help of a non-direction antenna. |
