The satellite which appears stationary relative to earth is called geostationary or geosynchronous satellite, communication satellite. A geostationary satellite always stays over the same place above the earth such a satellite is never at rest. Such a satellite appears stationary due to its zero relative velocity w.r.t. that place on earth.The orbit of a geostationary satellite is known as the parking orbit.
Important points:
It should revolve in an orbit concentric and coplanar with the equatorial plane.
It sense of rotation should be same as that of earth about its own axis i.e., in anti – clockwise direction (from west to east).
Its period of revolution around the earth should be same as that of earth about its own axis.
T = 24 hrs. = 86400s
Height of geostationary satellite
As T = 2π √ (r³/ GM) ⇒ 2π √ [(R + h)³/ GM] = 24 hr.