A communications satellite (sometimes abbreviated to Comsat) is an artificial satellite stationed in outer space for the purposes of telecommunications. Modern communications satellites use a variety of orbits including geostationary orbits, other elliptical orbits and low (polar and non-polar) Earth orbits. For fixed services, communications satellites provide a microwave radio relay technology complementary to that of fiber submarine communications cables. They are also used for mobile applications such as communications to ships, vehicles, planes and hand-held terminals, and for TV and radio broadcasting, for which application of other technologies, such as cable, is impractical or impossible.
The main problem with microwave communications is that the curvature of earth, mountains and other structures often block the line-of-sight. Due to these reason, several repeater stations are normally required for long distance transmission which increases the cost of data transmission between two points. This problem is removed by using communications satellite which are relatively newer and more promising data transmission media.
A communications satellite is basically a microwave radio relay placed in outer space. These satellites are launched either by rockets or by space shuttles and are precisely positioned 36000 kms above the equator with an orbit speed that exactly matches the earth’s rotation speed. Since a satellite is positioned in geosynchronous orbit, it is stationary corresponding to earth and always stays over the same point on ground. This allows ground station to aim its antenna at a fixed point in the sky. Dozens of satellite are now in orbit to handle international and domestic data, voice and video communication needs. The Indian satellite, INSAT-1B is positioned in such a way that it is accessible from any place of India. The main advantage of communications satellite is that it is single microwave relay station visible from any point of a very long distance. For example, satellite used for national transmission is visible from any part of the country. Thus transmission and reception can be between any two randomly chosen places in that area. Moreover, transmission and reception costs are not dependent upon distances between two points. In addition to this, a transmitting station can receive back its own transmission and check weather the satellite has transmitted the information correctly or not. If an error is detected, the data would be retransmitted. Hence necessary security measures are to be taken to prevent unauthorized tampering of information.The nature of future communications satellite systems will depend on the demands of the marketplace (direct home distribution of entertainment, data transfers between businesses, telephone traffic, cellular telephone traffic, etc.); the costs of manufacturing, launching, and operating various satellite configurations; and the costs and capabilities of competing systems - especially fiber optic cables, which can carry a huge number of telephone conversations or television channels. In any case, however, several approaches are now being tested by satellite system designers.
The main problem with microwave communications is that the curvature of earth, mountains and other structures often block the line-of-sight. Due to these reason, several repeater stations are normally required for long distance transmission which increases the cost of data transmission between two points. This problem is removed by using communications satellite which are relatively newer and more promising data transmission media.
A communications satellite is basically a microwave radio relay placed in outer space. These satellites are launched either by rockets or by space shuttles and are precisely positioned 36000 kms above the equator with an orbit speed that exactly matches the earth’s rotation speed. Since a satellite is positioned in geosynchronous orbit, it is stationary corresponding to earth and always stays over the same point on ground. This allows ground station to aim its antenna at a fixed point in the sky. Dozens of satellite are now in orbit to handle international and domestic data, voice and video communication needs. The Indian satellite, INSAT-1B is positioned in such a way that it is accessible from any place of India. The main advantage of communications satellite is that it is single microwave relay station visible from any point of a very long distance. For example, satellite used for national transmission is visible from any part of the country. Thus transmission and reception can be between any two randomly chosen places in that area. Moreover, transmission and reception costs are not dependent upon distances between two points. In addition to this, a transmitting station can receive back its own transmission and check weather the satellite has transmitted the information correctly or not. If an error is detected, the data would be retransmitted. Hence necessary security measures are to be taken to prevent unauthorized tampering of information.The nature of future communications satellite systems will depend on the demands of the marketplace (direct home distribution of entertainment, data transfers between businesses, telephone traffic, cellular telephone traffic, etc.); the costs of manufacturing, launching, and operating various satellite configurations; and the costs and capabilities of competing systems - especially fiber optic cables, which can carry a huge number of telephone conversations or television channels. In any case, however, several approaches are now being tested by satellite system designers.
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