Communication Satellites
Wireless transmissions used electromagnetic waves as the medium for carrying information, which require direct line-of-sight paths to the receiver. Thus their use for communication is limited by a variety of factors, among them the earth’s curvature. The location of transmitters in elevated positions helped to correct for the deficiency, and higher elevation was a goal of radio transmitter designers for decades. In 1960 the American National Aeronautics and Space Administration launched a weather balloon named Echo One, which had an aluminized reflective surface, to act as a reflector for radio signals. Echo One was an example of a passive satellite.
Passive satellites are simply reflectors, redirecting the radio signal which it receives in a designed direction. Active satellites receive and amplify the signal before sending it on to its next receiver. Active satellites are also known as relay satellites. In the early 1960s a consortium which included AT&T, Bell Laboratories, and NASA from the United States, the General Post Office of the United Kingdom (GPO), and the National Ministry for Posts, Telegraphs, and Telephones (PTT) of France created Telstar. Telstar was the first active communication satellite, launched from Cape Canaveral in 1962. Its first publicly viewable images were relayed in July of that year.
The first televised images to be shown was the Statue of Liberty and the Eiffel Tower. Because the broadcast began before President Kennedy was prepared to deliver his remarks the first broadcast relayed by satellite was a part of a baseball game being played between the Chicago Cubs and the Philadelphia Phillies, used by the engineers to pass the time before the planned program began. When President Kennedy did appear, his remarks led to the overnight strengthening of the US dollar in European markets. Later that same day Telstar relayed the first satellite overseas telephone call, between the Vice President of the United States and AT&T’s chairman in France.
By 1964 geosynchronous satellites – which remain in a fixed point above the earth – were orbiting and satellites were routinely relaying telephone, telegraph, radio, television, and telefax signals around the globe. Improvements to technology improved the quality of the signals to the point that transmissions were as clear as those sent over wire and cable on earth. The speed of the signal essentially circumnavigating the globe was nearly instantaneous. True duplex communication globally became a matter of routine as the 1960s and 1970s unfolded. World events could be monitored globally in real time, as they transpired.
Over 2,000 communications satellites were orbiting the earth by the end of the twentieth century, though many were no longer functional and merely waiting for their orbit to decay to the point that they would reenter the atmosphere and be destroyed. The satellites support virtually all forms of electronic communications on earth, for government, military, and commercial operations. New types of communication satellites with ever enhanced capabilities and service lives continued to be developed into the twenty-first century. They allow for near instantaneous communication around the globe.
