CLARKE ORBIT

If an artificial satellite is in a circular orbit 22,240 miles (35,784 km) above Earth, its speed will carry it around the world in almost exactly 24 hours. So, if the orbit is aligned with the equator, it will seem to hover motionless above a particular spot as Earth turns underneath, also in almost exactly 24 hours. Such a “geosynchronous” orbit is a perfect ar- rangement for aiming an antenna at the satellite.The antenna can be locked in place instead of requiring a complicated apparatus to make it move.Sir Arthur Charles Clarke, a British radio engineer, figured this out in the 1940s. He realized
that a signal transmitted by a satellite in such an orbit could be received by antennas over a very wide area on the ground, almost a third of the entire world. This was the beginning of communications satellites, which are a billion-dollar industry today. There are dozens of satellites at the proper height, and such an orbit is called a Clarke orbit.
Clarke had many innovative ideas about space travel and included them in some very imaginative science fiction novels, such as A Fall of Moondust, Rendezvous with Rama, and 2001: A Space Odyssey, which was made into a famous movie.