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The geostationary orbit , shortened GEO ( geostationary orbit ), sometimes called Orbit of Clarke, is an orbit located at 35  786 km of altitude above the equator of the Ground, in the equatorial plan and of a orbital Eccentricity null. It is a particular case of the geosynchronous Orbite. NB: concept of orbit " géostationnaire" do not exist; it is the satellite which is geostationary .

Characteristic

Its characteristic is that a body being on this orbit has a Period of revolution very exactly equal to the Period of rotation of the Earth on itself, that is to say 23:56 m 4.1s (it is the characteristic of the geosynchronous orbit), and appears motionless compared to any point at the surface of the Earth.

This characteristic is particularly important for the satellite S of Télécommunications or of diffusion of Télévision. The position of the satellite seeming motionless, equipment of reception provided with a fixed antenna pointing in the direction of the geostationary satellite will be enough to collect its emissions. For the cover of Europe, it is mainly Eutelsat which ensures this mission with many satellites in orbit.

This orbit is also used for the observation of the Earth since a fixed position in space. It is the case for the satellite weather geostationary, of which the Meteosat for Europe.

The geostationary satellites are necessarily located at the vertical or the zenith of a point of the equator or, in other words, are located in the equatorial plan of the Earth. Sometimes one hears wrongly of “geostationary satellite above Europe ”: it is necessary to understand by there satellite in visible geostationary orbit from Europe .

But the satellite will not remain stably with this position and will derive under the influence from several effects - of which the irregularities gravitational S and of the potential Géodynamique of the Earth, pressure of Solar radiation, etc - towards a position known as " cimetière" located towards 75 °E. The maintenance in geostationary position thus requires operations of correction of orbit into North-South and East-West, consuming Ergol S, their exhaustion being the main cause of end-of-life of the satellite.

It results from the preceding remark, that the geostationary orbit is an artificial human construction and that no celestial body (Astéroïde,…) cannot be there.

To join the geostationary orbit

The placement of a satellite in geostationary orbit is a complex operation which can take several weeks.

At the beginning, the satellite is on a geostationary Orbite of transfer.

See also: geostationary Orbit of transfer

; to supplement

Calculation of the altitude of the geostationary orbit

Calculation the speed of the satellite

See too

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