51Communication satellites and systems Part I 51.1-51.3.2 (Background)

51.1 Background

In 1883, Konstantin E Tsiolkovsky, a Russian schoolmaster ex­plained the principles of rocket flight in space. Twelve years later, he mentioned the possibilities of artificial satellites circling the earth outside its atmosphere. Half a century later, Arthur C Clarke wrote of orbiting radio relay stations (Clarke, 1945) and identified many of the advantages which satellite communication would have over terrestrial systems for long distance communication and broad­casting. Above all he pointed to the unique value of geostationary satellites.

Sputnik 1, the first man-made satellite, was put into low orbit (227km x 941km x 65.1°) in October 1957 and stimulated many other tests and demonstrations of practical applications for artificial satellites in the following years, above all for telecommunications. By 1962 the Telstar 1 (Dickieson, 1963) and Relay 1 (NASA, 1968) satellites had demonstrated long distance telephone links between fixed earth stations. By 1964 an experimental satellite, Syncom III, had been placed in an accurate geostationary orbit. In the same year INTELSAT, an international consortium having the objective of setting up a global satellite network for fixed telecommunications, came into being. By July 1965 the 'Early Bird' satellite, taken over by INTELSAT and later to be renamed INTELSAT I Fl, was in operation, relaying telephone calls between Europe and North America.

Much has happened since 1965. Satellites provide a major me­dium for linking together terrestrial telecommunications networks, province by province and country by country, using earth stations at fixed locations, typically with high gain antennas. INTELSAT has developed very extensively (Hall and Moss, 1978; Sachdev, 1990). INTERSPUTNIK became a second global system. Several regional systems, such as EUTELSAT, PALAPA and ARABSAT and many national networks are now in operation.

These systems have also become an important medium for the distribution of television programme material, to terrestrial broad­casting stations and more recently direct to home. In direct to the home television these satellites are competing, not only with terre­strial radio and cable broadcasting but also with newly emerging high power broadcasting satellites. And a substantial market has developed in the supply of satellite relay facilities for linking together networks of small, low cost earth stations on the users' premises.

There were early experiments with mobile earth stations as part of the NASA Applications Technology Satellite programme in the second half of the 1960s. The MARISAT system was set up by the Communications Satellite Corporation, starting in 1976, to provide telephone and data services by satellite to merchant ships. The internationally owned INMARSAT consortium took over that func­tion in 1982. More recently there has been widespread interest in satellite communication for airliners and for various kinds of mobile station on land; INMARSAT and a number of national systems are developing new facilities to meet these needs, often coupled with position finding aids.