Geo-Stationary Orbits
An object in such an orbit has an orbital period equal to Earth's rotational period one sidereal day, and thus appears motionless and fixed in space to ground observers. The concept of a geostationary orbit was popularised by science fiction writer Arthur C. Clarke in the 1940s as a way to revolutionise telecommunications, and the first satellite to be placed in this type of orbit was launched in 1963. Communications satellites are frequently placed in geostationary orbit so that Earth-based satellite antennas (located on Earth) do not have to rotate to track them but can be pointed permanently at the position in the sky where the satellites are located