Inclined orbit

from Wikipedia, the free encyclopedia

Inclined orbit (from English incline; dt. “To tilt”, “to hang at an angle”) generally refers to any orbit (orbit) with an orbit inclination (inclination) with respect to the equatorial plane of the orbiting celestial body .

Inclined geosynchronous orbit

Ground track : The "location" of the satellite "moves" above the ground.

Usually, however, the term is used to refer to a special geosynchronous orbit  ( GEO ) derived from geostationary orbit of an artificial earth satellite , the full name of which is inclined geosynchronous orbit . In this orbit, the orbital time is geosynchronous; This means that it corresponds exactly to the duration of the earth's rotation around its own axis (23 hours, 56 minutes, 4.09 seconds = 1  sidereal day ). The plane of the orbit is, however, inclined and slightly elliptical in relation to the equatorial plane - usually only slightly .

This orbit variant is often chosen to extend the deployment of geostationary satellites whose fuel supplies are running low, but which otherwise still function perfectly technically. A satellite in inclined orbit needs significantly less correction fuel to maintain its position, as otherwise most of the corrections made by a satellite in geostationary orbit are used to keep the inclination of the orbit at 0 °. As a result, the useful life of the satellite can be extended by approx. 1–2 years before it has to be brought into cemetery orbit. However, satellites in inclined orbit are no longer stationary above the horizon , as they move within 24 hours in the form of an  8 (see Fig.).

According to Kepler's first law , the orbital plane of the satellite must go through the center of gravity of the earth, which is why there is a north-south deviation. The period is one sidereal day. Because of the conservation of angular momentum , the trajectory is slightly elliptical. For an observer on earth , the satellite therefore oscillates between east and west with a period of half a sidereal day.

Satellites in inclined orbit can therefore not be received well with fixed parabolic antennas , such as those used in e.g. B. be used for private satellite reception. These satellites, which have already been financially depreciated, are therefore rented out for reduced fees for data transmission between professional ground stations , as these need antenna tracking anyway from an antenna diameter of 5 m (even in normal GEO satellites fluctuate slightly, which is why very large, strongly bundling antennas have to be tracked) and therefore can also correct the fluctuating position of the satellite.

Web links