Why are communication satellites placed in geostationary orbit?
A satellite placed at a height (above the equator) of approx 36000km will have an orbital period of 24 hours. It will therefore always “appear” to be in the same position above the Earth’s surface (geostationary). They have a set “footprint” and only cover a limited part of the surface. This means that any transmitting or receiving “dish” aerials once “set” will always point towards the satellite and do not need to “track” the satellite. The idea was first suggested by the science fiction writer Arthur C Clark in the 1940’s. In a polar orbit, the satellite moves at 90 degrees to the direction of the Earth’s rotation so cannot ever appear to be “geostationary”. They are excellent for mapping or surveying purposes however as they will eventually cover the entire surface of the Earth.
