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Satellite Communications Network
By Editor | February 11, 2008
A satellite communications network (also referred to as satcom network) is a system which enables communication through artificial satellites launched into space. Communications satellites (also abbreviated to comsat) are artificial satellites positioned in space for use in telecommunication. These satellites use different kinds of orbits like low (non-polar and polar) Earth orbits, elliptical orbits, Molniya orbits and geostationary orbits. This type of satellites 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 (more specifically geostationary 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, geostationary 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.
A satellite communications network 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. A satellite communications network also helps in communication in remote areas like mountains and near the poles.
A satellite communications network also enables 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.
A satellite communications network has more than one satellite. Satellites placed 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) are one way of forming a satellite communications network or a satellite constellation as they are called. Highly elliptic (HEO) and medium earth orbit (MEO) satellite systems can also be used for satellite communication. As one goes farther away from earth, the coverage of the satellites increases and thus lesser satellites are required. For instance, four HEO satellites can cover the earth whereas about ten MEO satellites would be required and about 24 low earth orbit (LEO) satellites though Iridium has 66 satellites. HEO and MEO satellites are still in a developmental stage. Iridium, Globastar and Inmarsat use LEO satellites for satellite communication. Molniya satellites are useful for telecommunication near the poles as geostationary satellites revolve around the equator. Molniya satellites are inclined for optimum use at the poles and are primarily used for telephony and TV services over Russia. The Global Positioning System (GPS), the European Galileo positioning system, the Chinese COMPASS navigation system and the Indian IRNSS are all Global Navigation Satellite Systems (GNSS) that make use of their own satellite communications network.
These are some basic details about satcom networks. For more detailed information about individual networks like the network operated by Iridium or other service providers, please look at more detailed articles dealing with specific satellite communication networks.
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