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Satellite Communications Systems - SatCom
By Editor | August 26, 2008
Satellite communications systems (or satcoms as they are referred to in short) help in providing a communication link. This is carried out through artificial satellites which are positioned in different kinds of orbits in space. Satellite communications systems use one or more of these five kinds of orbits – geostationary orbits, low (non-polar and polar) Earth (LEO) orbits, medium earth orbits (MEO), highly elliptical orbits (HEO) and Molniya orbits.
The satellites of satellite communications systems form a constellation or group of interlinked satellites. Molniya satellites, primarily used by Russia, are inclined for optimum use at the poles and are primarily used for telephony and TV services over Russia. Molniya satellites are used for satellite communication near the poles as geostationary satellites revolve around the equator. 4 to 6 geostationary satellites can cover the whole surface of the earth. More satellites are needed for highly elliptic and medium earth orbit satellite systems. About 24 low earth orbit satellites would be needed in an LEO constellation though Iridium has 66 satellites in their satellite constellation.
Satellite communications systems provide not only telephone services but also internet and other telecommunication related services like television services. Satellite broadband and satellite television are enabled by satellite communications systems. Satellite radio is also made possible by it. Then there are the Orbital Satellite Carrying Amateur Radio (OSCAR) satellites which are geared specifically for amateur radio operators.
The satellite phone remains the most important service provided by satellite communications systems. Some popular satellite phone operators are Iridium, Globastar and Inmarsat. Satellite phones are very useful for frequent fliers or for those who work in remote locations like forests, mountains or near the polar caps.
Satellite communications systems make use of satellites in space rather than physical cables connecting the two centres of communication. So, with satellite communication, it is theoretically and in most cases practically possible to connect any two points on earth. With many services being carried out through the internet, telecommunications have started to play a major role in our daily lives and global satellite communications are important means of communication in the modern world.
Satellite communication is most useful where it is not practical to use fibre optic submarine communication cables (cables laid in oceans and seas for communication across continents) like for use in planes, ships, vehicles, hand held gadgets, TVs and radios. Fixed Service Satellite (FSS) is now being replaced by Direct Broadcast Satellite (DBS) in some countries for satellite television. Satellite telephones make use of MSS. The three major kinds of MSS are aeronautical MSS (AMSS), land MSS (LMSS) and maritime MSS (MMSS).
Satellite communication was initially used primarily for telecommunication between countries and across continents. Telegraphs and telephones relied on satellite communication till the popularity of submarine communication cables. However, satellite communication still serves to connect remote islands, where submarine communication cables have not been laid down, like Saint Helena, Ascension Island and the Pacific islands. Satellite phones use geostationary satellites or low earth orbit satellites to communicate.
Topics: Satellite Communications |