Victor Thomas, age 15, of Albuquerque, N.M. for his question:
WHEN WAS THE FIRST COMMUNICATIONS SATELLITE USED?
A communications satellite is any earth orbiting spacecraft that provides communication over long distances by reflecting or relaying radio, television or laser signals. The first commercial exploration of communications satellites was started in the United States by the Communicatons Satellite Corp. (Comsat), which was incorporated on Feb. 1 , 1963.
In August 1964 the International Telecommunications Satellite Organization (Intelsat) was formed, of which Comsat became the U.S. member. Based in Washington, D.C., Intelsat is owned by 105 nations.
Early Bird, or Intelsat 1, launched in April 1965, was the first Satellite of Intelsat and it provided 2,400 voice channels and one television channel between the U.S. and Europe. During the 1960s and 1970s, message capacity and transmission power of the active communications satellites were greatly increased.
The first satellite of the Intelsat 4 series, launched in 1971, provided 4,000 voice circuits. The Intelsat 5 satellites (a series of nine, the first of which was launched in December 1980) have a capacity of 12,000 voice circuits, which can be replaced in part or completely by high quality color television.
Present day commercial satellites provide a wide range of services. Television programs are relayed to cable systems throughout the U. S. and digital data are transmitted 100 times faster than by the best quality land lines.
The International Maritime Satellite Organization (Marisat), founded in July 1979, provides telex, telephone and digital data links between ships, offshore facilities and shore stations that are distributed all over the world.
Satellite Business Systems (SBS) is owned by Comsat, IBM and Aetna. The first SBS satellite was launched in November 1980 and it offers high speed digital and voice TV linkages.
Because of the number of ground stations making use of the same satellite is increasing, new techniques have been introduced to augment the message capacity of communications satellites. The time division multiple access method (TDMA) allows a large number of ground stations to make use of the same channel by assigning time slots during which each ground station can communicate with the satellite.
An effective method for the handling of a large number of ground stations is the scanning beam technique, which combines the advantages of frequency reuse and the TDMA technique.
The use of laser beams for communications with passive or active satellites is currently under development. Laser beams permit a much larger message capacity than do radio beams.
Laser beam and particle beam technology is also being developed for use in military satellites as part of a new defense strategy proposed in 1983 by President Ronald Reagan.