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Mobile Satellite Communications and MSS
By Editor | August 12, 2008
Mobile satellite services (MSS), also known as mobile satellite communications, are commonly referred to as satellite communication systems that use portable terrestrial terminals rather than fixed satellite services (FSS). FSS use fixed terrestrial terminals where the location of the ground stations do not change frequently. Consumer satellite television (or cable television) uses FSS. MSS terminals may be placed in planes, ships and vehicles or may be carried by individuals. Satellite telephones use MSS. The three major kinds of MSS are as follows: land MSS (LMSS), aeronautical MSS (AMSS) and maritime MSS (MMSS).
Satellite telephones form the largest sector of mobile satellite communications. Satellite phones use low (non-polar and polar) Earth orbits or geostationary satellites. Mobile satellite communications is described as radiocommunication between space stations and mobile earth stations, or between space stations, or between mobile earth stations by using one or more space stations.
Mobile satellite services help primarily in connecting stations which are not otherwise contactable through either submarine communication cables or any other form of land communication services. Therefore mobile satellite service helps in communication from places like planes (AMSS), ships (MMSS), and even cars (LMSS) if one is travelling in remote areas. Also, places like mountains or the countryside where there are no cellular phone operators’ towers or no other form of telecommunication, satellite phones come in handy because of the reason that they depend on space satellites for communication and are not dependent on local satellite communication towers or physical communication cables. Iridium, Globastar and Inmarsat are some of the more popular mobile satellite service providers. Satellite phones, by their very nature, have a global connectivity. The connectivity is not dependent on terrestrial location. Some mobile satellite services do not use geostationary satellites (because the cost of geostationary satellites is high). Instead they opt for multiple low earth orbit (LEO) satellites. A group of such LEO satellites all participating in a specific purpose is known as a satellite constellation. The Chinese COMPASS navigation system, the Global Positioning System (GPS), the Indian IRNSS , the European Galileo positioning system are all Global Navigation Satellite Systems (GNSS) that use mobile satellite communications.
Medium earth orbits and highly elliptic orbits can also be used for mobile satellite services rather than of low earth orbits. The farther away from earth one goes, greater is the coverage of the satellites and therefore lesser satellites are required. For example, four HEO satellites may cover the earth whereas about ten MEO satellites may be necessary and about 24 LEO satellites though Iridium uses 66 satellites. MEO and HEO satellites are still in am early stage of development. Globastar, Iridium and Inmarsat use LEO satellites for mobile satellite communications.
CASSIOPE communications satellite of Canada’s CASCADE system plans to offer discontinuous coverage where LEO satellites will receive data while travelling over one part of the globe and transmit it when they pass over the destination. Orbcomm also plan to use this store and forward method of mobile satellite service.
Mobile satellite communications help in connecting remote islands that are not connected to the rest of the world through fibre optic submarine communication cables like the Pacific Islands, Saint Helena and Ascension Island.
Topics: Mobile Satellite Communications |