Satellite Communications System
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#* 6® Project Echo and the Telstar® experiments were pioneering steps in the development of a global satellite communications system. As successful ventures in government-private enterprise cooperation, they were tangible evidence of the Bell System's constant effort to create new and b e t t e r c o m m u n i c a t i o n s f o r t h e n a t i o n it serves. Operational communications by satellite is a reality today. The hundreds of Bell System people who contributed to the success of the Echo and Telstar projects are justifiably proud of the role they played in bringing people of different lands into closer contact with one another. .. America's new star in the skies bears one other indisputable and praiseworthy distinction. It is a work oi peace, Telstar threatens no one, menaces no one, does not carry within itself the potential of disaster. It seeks to build, not to destroy. All those who had a hand in putting it into space can view their work with satisfaction, and the country in which it was developed can present it to Excerpt from an editorial tliat appeared in the New York Herald Tribune on July 11, the world with pride ..." 1 9 6 2 , t h e d a y a f t e r Te l s t a r I w a s l a u n c h e d . satellite communicetions-tiie deginnlngs Communication by satellites orbiting the earth was considered to be pure science fiction only a quarter of a century ago. Even the very idea of launching a satellite into space then seemed, in terms of years, remote indeed to the scientific community. Yet in 1945, Arthur C. Clarke, a noted English scientist and writer, seriously suggested such an idea in an article published in Wireless World, Clarke envisioned a manned satellite in space acting as a relay station for television signals between continents. Although this proposal seemed far in advance of its time, events were soon to catch up A. ^ ^ to and even by-pass many of the initial theories. □ On January 11,1946, the U.S. Army Signal Corps facility at Ft. Monmouth, N. J., began a series of tests known as Project Diana. During these experiments, microwave radar signals were bounced off the moon and back to earth again, proving for the first time, that relatively low power could transmit signals over extremely long distances. □ Dr. John R. Pierce of Bell Telephone Laboratories advanced proposals for a space satellite communications system in a formal paper delivered at Princeton University in November 1954. Five months later, Pierce's concept, similar to what was to eventually embody the Telstar experiments, was published in Jet Propulsion magazine under the title, "Orbital Radio Relays." □ On October 4,1957, the Soviet Union astounded the world and catalyzed United States space efforts by launching and successfully putting into orbit the first satellite. Sputnik I. This scientific breakthrough was followed only a month later with the successful orbiting of Sputnik II. The real research and development work on satellite communications now began in earnest. □ The United States formally entered the "Space Age" on January 31, 1958, when the U.S. Army successfully launched Explorer I into orbit. Five months later. Congress, now fully aware of the critically important scientific and political implications of this new frontier, passed the National Aeronautics and Space Act, setting up the National Aeronautics and Space Agency (NASA). One of the principal areas of endeavor for this new agency was to be satellite communications experimentation. □ Score, the first satellite to be used for voice communications, was launched by the U.S. Air Force on December 18, 1958. Score was equipped with tape recorder units that transmitted prerecorded messages back to earth on receipt of signals. The day after it was launched, a Christmas greeting to the world recorded by President Eisenhower was transmitted. Score continued to transmit for 12 days before its batteries became too weak for further use. □ Project Moonbounce, which carried the experiments of Project Diana several steps further, was the predecessor to the forthcoming Echo experiments. In November 1959, scientists at Bell Telephone Laboratories' Holmdel, N. J., location and at the Jet Propulsion Laboratories in Goldstone, California, accomplished live voice transmission by using the moon some 250,000 miles away as a passive reflector. Signals were bounced off the moon, received, and understood on the opposite side of the continent. The transmission delay was about six seconds. Altogether, 17 moon-bounce tests were successfully conducted. echo I-the first passive communications sateiiite The Bell System's role in satellite communications experimentation began in the early morning hours of August 12, 1960, at Cape Canaveral (now Cape Kennedy), Fla. A Thor-Delta missile was launched on that day with the world's first passive communications satellite intricately folded and tucked away in a capsule underneath its nose cone. The missile was commanded and guided by a system designed by a Bell Laboratories-Western Electric team. □ Echo I, an inflated ten-story-high balloon, was put into a circular orbit around the earth approximately 1,000 miles up. Its speed was more than 16,000 mph. The balloon was made of an aluminized Mylar-coated skin half as thick as the cellophane on a cigarette package. □ Some 80 minutes after launch. Echo I was spotted over Woomera, Australia. A half hour later it was picked up at Goldstone, California, and seven minutes after that Bell Laboratories engineers at Holmdel picked up the balloon's reflection of Goldstone's radio beam. (Upper Left) The receiving horn antenna used in both Project Echo and Telstar experiments at Holmdel, N.J. (Left Center) The Delta space vehicle with the 100-foot deflated "Echo I" satellite canister shown on top of rocket. (Lower Left) Ten-story-high Echo I Satellite. The sphere was made of .0005-inch thick Mylar plastic coated with aluminum. (Right) Bell Laboratories William C. Jakes (hand on belt) awaits confirmation of transmission test on the Echo I satellite. o In the ensuing weeks, a number of two-way telephone conversations as well as transmission of music and data were sent between Holmdel and Goldstone using this balloon as a passive relay station in the sky. Communi cations were also made to other points in the United States and Europe. □ Echo I continued to be used for many weeks, demonstrating that a passive satellite would work and providing valuable data for future experiments in satellite communication. After several months, the once-smooth balloon, punctured by tiny meteorites, shriveled in space, thus reducing its effectiveness as a radio mirror. □ Project Echo, a joint undertaking by the Bell System, The Jet Propulsion Laboratories and NASA, was the first major effort in an experi ment to study long-range communications using an orbiting earth satellite. The success of these experiments was due in large part to extensive research and development efforts carried on over the years at Bell Laboratories. □ A horn-reflector antenna originally designed for cross-country radio relay proved adequate to scoop up the tiny microwave reflection (millionths of a billionth of a watt) expected from Echo. Engineers employed a method of receiving microwave signals known as wideband frequency modulation with negative feedback. Invented 23 years before at Bell Laboratories and little used until then, this method was employed with modern circuitry at Holmdel and Goldstone and performed well. New types of low-noise amplifiers using solid-state masers gave excellent results. For example, a ruby maser, unlike previous amplifiers, created virtually no radio "noise" Transmitting antenna used on Project Echo experiments. of its own and enabled scientists to "hear" the very tiniest of signals from outer space. And tracking of the satellite by electronic computers, by radar, and by telescope proved to be extremely reliable. □ Project Echo was undoubtedly the first important milestone in the development of an operational satellite communications system. The success of these experiments caught the imagination of the world. People in distant lands were fascinated as night after night they watched this 100-foot-high silverized balloon, clearly visible to the human eye, streak past in the sky overhead. □ Stripped of its dramatics, however. Project Echo was the first practical demonstration of extending communications facilities into space. The stage was now set for the first Telstar experiment. the teistar project is hern The success of the Echo experiments, coupled with new technological advances at Bell Laboratories, prompted the American Telephone and Telegraph Co., parent unit of the Bell System, to continue experiments in satellite com munications on a much broader scale. In January 1961, AT85T was authorized by the Federal Communications Commission to establish an ex perimental communications link across the Atlantic Ocean. Two 170-pound active repeater satellites were to be launched by NASA^ and all launching costs were to be paid by AT&T. In addition to enlarging facilities .at Holmdel, N. J., a new satellite communications ground station would be built in Maine. □ During these forthcoming experiments, a microwave signal would be beamed from a ground station to the satellite. The satellite would pick up the signal, amplify it, and retransmit it back to earth again on a different frequency. The recently completed Echo experiment involved the transmission of only one two-way telephone conversation at any one time. These new experiments would be aimed at transmitting a broadband signal capable of carrying a number of voice or data channels, or alternately, a single live television signal. □ Thus, the Teistar project was born. Eventually, it would involve As satellite (1) comes over the horizon, the efforts of more than 1,000 people in the Bell System, including some the Command Tracker ( 2 ) acquires the satellite, and passes hold information 400 scientists, engineers, and technicians at Bell Laboratories.