History of Satellite Communications

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History of Satellite Communications

The first idea of satellite communication came from an article in 1945 named Wireless World, where Author C. Clarke described the use of manned satellites in 24 hour orbits to distribute television programs. However, the first person to carefully evaluate the technical and financial aspects of such a venture was John R. Pierce of Bell Telephone Laboratories (Whalen, n.d.).

In a 1954 speech and 1955 article, Pierce described the usefulness of a communications "mirror" in space, a medium-orbit "repeater" and a 24-hour-orbit "repeater." In comparing the communications capacity of a satellite, which he estimated the capacity at 1,000 simultaneous telephone calls, and the capacity of the first trans-atlantic telephone cable, which could carry 36 simultaneous telephone calls at a cost of 30-50 million dollars, Pierce wondered if a satellite would be worth a billion dollars (Whalen, n.d.).

By the middle of 1961, RCA had a contract with NASA to build, a 4000 mile high, medium-orbit, active communications satellite called RELAY, AT&T was working on its own medium-orbit satellite called TELSTAR, and Hughes Aircraft Company had an exclusive contract to build a 24-hour orbit, 20,000 mile high satellite, called SYNCOM. By 1964, two TELSTARs, two RELAYs, and two SYNCOMs had operated successfully in space. The transponder technology used by AT&T in the TELSTAR I satellite is current technology in use today (Whalen, n.d.).

On April 6, 1965, a new company called COMSAT launched its first satellite, EARLY BIRD, from Cape Canaveral beginning Global satellite communications. The EARLY BIRD satellite provided almost 10 times the capacity of submarine telephone cables for almost 1/10th the price. Satellites are still competitive with cable for point-to-point communications, but the future advantage may lie with fiber-optic cable (Whalen, n.d.).

How Satellites Work

Orbit

First, as one would guess, satellites are launched into orbit. There are several types of orbit for satellites to follow but the main three are Low Earth Orbit (LEO), Medium Earth Orbit (MEO), and Geosynchronous Orbit (GEO). Satellites in a Low Earth Orbit are 100-300 miles above the earth's surface, and it must travel around 17,500 mph, circling the planet in about 10 minutes, to avoid gravity pulling them back to earth. In a Medium Earth Orbit, a satellite is 6,000–12,000 miles above the earth and will circle the planet 4 to 6 hours. The Geosynchronous Orbit is a bit more complex, this orbit is 22,282 miles above the earth.

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