Geostationary satellite

Definition
According to Kepler's Third Law, the orbital period of a satellite in a circular orbit increases with increasing altitude. Space stations and shuttles in Low Earth orbit (LEO), typically two or four hundred miles above the Earth's surface make between fifteen and sixteen revolutions per day. The Moon, at an altitude of about 240,000 miles (385,000 km), takes thirty days to make a complete rotation. Between those extremes lies the "magic" altitude of 22,300 miles (35,786 km) at which a satellite's orbital period matches, or is an integral part of, the period at which the Earth rotates: once every sidereal day (23 hours 56 minutes). In that case, the satellite is said to be geosynchronous.

If a geosynchronous satellite's orbit is not exactly aligned with the equator, the orbit is known as an inclined orbit. It will appear (when viewed by someone on the ground) to oscillate daily around a fixed point in the sky. As the angle between the orbit and the equator decreases, the magnitude of this oscillation becomes smaller; when the orbit lies entirely over the equator, the satellite remains stationary relative to the Earth's surface – it is said to be geostationary.