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Geosynchronous orbit

Geosynchronous orbit.

Geosynchronous and Geostationary Orbit

A geosynchronous orbit may be defined as one with an orbital period (the time needed to orbit once around the Earth) that matches the rotation rate of the Earth. This is a sidereal day, which is 23 hours 56 minutes and 4 seconds in length, and represents the time taken for the Earth to rotate once about its polar axis relative to a distant fixed point. This is about four minutes shorter than the common day length of 24 hours, which is relative to the sun.

A geostationary orbit is a special case of a geosynchronous orbit. A satellite is in a geostationary orbit when it appears stationary from the point of view of an observer on the Earth's surface. This can only occur when:

  • The orbit is geosynchronous
  • The orbit is a circle
  • The orbit lies in the plane of the Earth's equator

Thus, a geosynchronous satellite will be geostationary only with the additional restrictions of it being in a circular orbit situated over the equator.

The following parameters are always true for any geostationary satellite:



Height above equator

35,785 km (22,236 miles)

Orbit radius

42,155 km (26,194 miles)

Orbit circumference

264,869 km (164,582 miles)

Arc length per degree

736 km (457 miles)

Orbital velocity

11,066 km/hr= 3.07 km/sec (6,876 miles/hr)

Source: Eumetstat