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Satellite Communications - Satcom
By Editor | February 29, 2008
Satellite communications (or satcom as it is abbreviated as) is communication through means of artificial satellites put in space. Satcom was also the name of a series of communications satellites (also referred to as comsats) originally developed and operated by RCA American Communications (RCA Americom). Satcom was one of the earliest geostationary satellites. While the first Satcom, Satcom 1 was launched on December 13, 1975, the last Satcom, Satcom K2, was launched on November 27, 1985 and was de-orbited in February 2002. Satcom was initially superseded and then replaced by the GE satellites.
The idea of satellite communications and satellites in geostationary orbits (orbits so high that though the satellite revolves around the earth in that orbit, they appear stationary to an observer on earth) was first proposed by the science fiction writer Arthur C. Clarke. Satellite communications is most useful where it is not practical to use fibre optic submarine communication cables (cables laid in seas and oceans for communications across continents) like for use in ships, planes, vehicles, hand-held gadgets, TVs and radios.
Communications satellites were used initially primarily for telecommunication between countries and across continents. Telegraphs and telephones relied on communications satellites till the popularity of submarine communication cables. However, global communication satellites still serve to connect remote islands, where submarine communication cables have not been laid down, like Saint Helena. Satellite phones (which remain popular) use geostationary satellites or low earth orbit satellites to communicate.
Satellite communications is used for satellite television and also for worldwide radio stations. Fixed Service Satellite (FSS) is now being replaced by Direct Broadcast Satellite (DBS) in a lot of countries for satellite television.
Satellite communications is also used for internet access where wireline broadband or dial-up internet connections are not possible. Ships, planes and vehicles are some of the places where satellite internet connections are used. Satellite communications is also possible in remote areas like mountains and near the poles.
Communications satellites also enable global positioning systems (GPS) which help to find the precise location, speed, time and direction of a body (or rather a GPS receiver) anywhere on earth.
The satellites operate in different kinds of orbits. The two most common types are geostationary orbits and low to earth (LEO) orbits. Whereas 4 satellites placed in a geostationary orbit can cover the entire earth, about 24 satellites are needed to cover the entire surface of the earth if the satellites are placed in LEO orbits. The satellite communication major Iridium Satellite LLC has 66 LEO satellites and also a few spare satellites in orbit so that they can replace any non-functional satellites. The system of inter-related satellites is known as a satellite constellation and Iridium requires 66 satellites to complete its constellation.
The most popular use of satellite communications is in satellite phones (also referred to as sat phones). Satellite phones work on the principle of global connectivity even on water or in an aeroplane as instead of fibre optic submarine communication cables it uses satellite communication. Satellite phones are especially useful for frequent fliers or those working in remote locations.
Topics: Satellite Communications |