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In a 1945 article in Wireless World, Arthur C. Clarke described a system of “extraterrestrial relays” or repeaters in space. He noted that three such repeaters located 36,000 km above the equator, 120 degrees apart would cover the entire globe. Only 12 years later, the Soviets launched Sputnik, a satellite that simply beeped, but spurred US scientists and engineers to develop more sophisticated satellites for commercial use. In 1965, the first commercial international satellite, known as Early Bird or Intelsat I, was launched to link North America and Europe. Today, there are numerous satellites that provide global, regional, or national coverage. Satellites serve nations including Australia, Brazil, Canada, China, India, Indonesia, Russia, and the US, and regions such as North America, Africa, East Asia, Southeast Asia, and South Asia.
Satellite technology has evolved dramatically since the early 1960s. Early Bird had only 240 telephone circuits, while today’s geostationary satellites have 24–72 transponders, each capable of carrying a high-definition TV channel, or multiple television channels, or thousands of telephone calls, text, and data messages. Satellites offer several advantages. They can serve rural and remote areas because earth stations can be installed virtually anywhere. Satellite networks are highly reliable; a problem with an earth station affects only that location. Satellite capacity is also flexible; for example, a community can begin with a few voice circuits, and then add more capacity for Internet access and television reception. The cost of communication via satellite is independent of distance. A disadvantage of geostationary (GEO) satellites for interactive services (such as telephony) is latency or delay from transmitting to and from the satellite. Low earth orbiting (LEO) satellites have no noticeable delay because they are located only about 1000 km above the earth. At this altitude, numerous satellites in various orbits must be used to provide continuous coverage.
The most common use of satellites is for television transmission such as news feeds and major sporting events such as the Olympic Games and the World Cup. Satellites transmit television signals to local television stations for terrestrial rebroadcast or to distribution through cable networks. High-powered GEO systems transmit satellite signals to satellite dishes on houses or apartments. Satellites can also be used for global telephone service. Internet access including broadband can also be provided by satellite, either directly to end users or through satellite gateways.
In developing regions, satellites can help to close the digital divide by providing access to the Internet and broadband. Very small aperture terminals (VSATs) operating with GEO satellites can be used for interactive voice and data, as well as for broadcast reception. VSATs are also used for telephony and Internet access in Alaska and the Australian Outback. Banks in remote areas of Brazil are linked via VSATs; microfinance offices in African villages linked via satellite allow people to transfer or withdraw funds. Satellites can also be used for telemedicine and distance education. In Alaska, village health aides communicate daily via satellite with physicians at the regional hospitals. The University of the South Pacific uses a satellite-based network to provide tutorials to correspondence students scattered in 12 island nations of the South Pacific from its main campus in Fiji. The University of the West Indies links its campuses in Jamaica, Barbados, and Trinidad with extension centers throughout the Caribbean. The Inuit Broadcasting Corporation (IBC) in the Canadian Arctic was the first indigenous media project in the world to broadcast by satellite.
Satellite communications have had dramatic impacts in ending isolation and creating a truly global village. But will satellites survive, as companies install more optical fiber, and terrestrial wireless networks link computers and mobile phones? Satellites will still have roles to play, particularly for broadcasting and in developing regions. Satellites will remain an important means of transmitting video and between continents. They will also serve as a backup for submarine cables if cables are cut or circuits are overloaded. In the developing world, satellites will deliver television and radio signals and provide broadband Internet access.
Bibliography:
- Clarke, A. C. (1945). Extra-terrestrial relays: Can rocket stations give world-wide radio coverage? Wireless World, 51, 305–308.
- Elbert, B. R. (2006). Introduction to satellite communication. Norwood, MA: Artech.
- Hudson, H. E. (ed.) (1985). New directions in satellite communications: Challenges for north and south. Norwood, MA: Artech.
- Hudson, H. E. (1990). Communication satellites: Their development and impact. New York: Free Press.
- Hudson, H. E. (2006). From rural village to global village: Telecommunications for development in the information age. Mahwah, NJ: Lawrence Erlbaum.
- Pelton, J. N., Oslund, R. J., & Marshall, P. (eds.) (2006). Communications satellites: Global change agents. Mahwah, NJ: Lawrence Erlbaum.
- Pelton, J. (2011). Satellite communications. Berlin: Springer.