IV.

Commercial Communications Satellites

Deployment and operation of communications satellites on a commercial basis began with the founding of the Communications Satellite Corporation (COMSAT) in 1963. When the International Telecommunications Satellite Organization (Intelsat) was formed in 1964, COMSAT became the US member. Based in Washington, D.C., Intelsat is owned by more than 120 nations. Intelsat 1, known as Early Bird, launched in 1965, provided either 2,400 voice circuits or one two-way television channel between the United States and Europe. During the 1960s and 1970s, message capacity and transmission power of the Intelsat 2, 3, and 4 generations were progressively increased by beaming the satellite power only to the Earth and segmenting the broadcast spectrum into transponder units of a certain bandwidth.

With the launch of the Intelsat 3 satellites in 1969, full global coverage was achieved for the first time, covering each of the three main oceans. With the Intelsat 5 series (1980), introduction of multiple-beam operation resulted in additional increases in capacity. A satellite’s power could now be concentrated on small regions of the Earth, making possible smaller-aperture (coverage area), lower-cost ground stations. An Intelsat 5 satellite can typically carry 12,000 voice circuits. The Intelsat 6 satellites, which entered service in 1989, can carry 24,000 circuits and feature dynamic on-board switching of telephone capacity among six beams, using a technique called SS-TDMA (satellite-switched time division multiple access).

By the early 1990s, Intelsat had 15 satellites in orbit, providing the world’s most extensive telecommunications system. Other systems also provide international service in competition with Intelsat. In 1997 all regulatory restraints to such competition were lifted. The growth of international systems has been paralleled by domestic and regional systems, such as Europe’s Eutelsat and Telecom, and America’s Telstar, Galaxy, and Spacenet programmes.