Geosynchronous orbit

An Earth orbit with a period equal to Earth’s sidereal rotation period, about 23 hours 56 minutes. A satellite returns to the same position in the sky at the same sidereal time each day.

Orbital period: The time an orbiting body takes to complete one revolution around its primary. Matching this period to Earth’s sidereal rotation defines a geosynchronous orbit.
Communications satellite: An artificial satellite that relays signals between distant locations on Earth or in space. Geosynchronous placement can maintain continuous visibility of a broad ground region.
Low Earth orbit: An Earth orbit at relatively low altitude, typically below about 2,000 kilometers. Its short orbital period means satellites pass over locations rather than remaining in view all day.
Geostationary belt: The circular equatorial region at geostationary altitude occupied by geostationary satellites. Limited useful orbital slots along this belt create coordination and spacing constraints.
Kepler's laws of planetary motion: Three laws describing how bodies orbit under gravity, including the relation between orbital period and orbit size. Kepler’s third law links the geosynchronous period to its characteristic orbital radius.
Weather satellite: A satellite that observes atmospheric and surface conditions to support weather monitoring and forecasting. Geostationary weather satellites repeatedly image the same hemisphere from geosynchronous altitude.
Medium Earth orbit: An Earth orbit between low Earth orbit and geosynchronous altitude. Navigation satellites often use this lower-altitude alternative with periods shorter than one sidereal day.
Satellite station-keeping: Orbital maneuvers that counter perturbations and keep a satellite within its assigned position or orbit. Geostationary satellites need station-keeping to remain near their assigned sky locations.
Inclination: The angle between an orbit’s plane and a chosen reference plane. A tilted geosynchronous orbit makes its satellite appear to move north and south each day.
Satellite television: Television distribution that uses satellites to transmit programming to receiving dishes. A geostationary satellite can serve fixed dishes without requiring them to track across the sky.

Linked from 2 pages