Communications Satellites, Technology of

Abstract

In 1895, a Russian scientist, Konstantin Tsiolkovsky, gave the world its first vision of a stationary satellite. He observed that an object orbiting Earth at 22,300 miles up would match the angular rotation of Earth and thus provide a seemingly stationary “star” overhead. Fifty years later, Arthur C. Clarke expanded on this vision. In 1945, he indicated that such an object orbiting Earth at 22,300 miles up must also have its orbit in the equatorial plane to be considered stationary. Clarke called the object a “satellite” and further noted that providing a satellite in this orbit with a communications repeater could produce a very valuable communications capability. Clarke named such satellites “geostationary communication satellites.” Clarke postulated that three geostationary satellites spaced 120° apart would provide full global communications coverage for telephone and television service to the world's population. Clarke's concept was ahead of the technologies needed to make it a reality. This article gives the history of communication satellites. In a few decades, communications satellites have become an indispensable part of the world’s communications infrastructure Orbits, communication links, on‐board antennas, ground antennas are discussed. Communication satellites have two different designs: spinner and body‐stabilized satellites new technology in digitization, power, propulsion, and systems are introduced.