Home GEO transfer

Geostationary Earth Orbit transfer

Your browser does not support the canvas element

Geostationary Earth Orbits

Exactly how high up are those geostationary satellites, and how do they get there? Here are very brief answers to these questions.

In order to orbit synchronously with the Earth, geostationary satellites have to be 42164 km above the centre of the Earth. As the Earth's radius is 6378 km this means the satellites must be 35786 km above the surface of the Earth. Satellites are launched as close as possible to the equator into a transfer orbit, which is an elliptical orbit reaching 35786 km above the Earth at its apogee (furthest point), but passing only a few hundred km above the surface of the Earth at its lowest point (perigee). Transfer to geostationary orbit occurs when at apogee, using a fuel burn to increase the velocity to that required for a circular orbit of radius 42164 km. [An elliptical orbit like this, used to move from one circular orbit to another, is called a Hohmann transfer orbit.]

This animation shows the Earth, viewed from above the North Pole, with a satellite starting at perigee and orbiting in an elliptical orbit until the Go to GEO button is clicked. The satellite then increases speed at its next apogee, into a circular orbit. The animation shows the scale of the orbit, so that the Earth and the path of the satellite are roughly in the correct proportions. The satellite itself is made much too large so it is easily visible.