Geostationary ring
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The geostationary ring is a volume segment around the geostationary orbit defined by variations in altitude and declination that can occur for uncontrolled objects left in the geostationary orbit.
The geostationary orbit is subject to orbit perturbations caused by anomalies in the gravitational field of the Earth, by the gravitational effects of Sun and Moon, and by solar radiation pressure.
A precessional motion of the orbit plane is caused by the oblatedness of the Earth (J2), and the gravitational effects of Sun and Moon. This motion has a period of about 53 years. The two parameters describing the direction of the orbit plane in space, the right ascension of the ascending node, and the inclination are affected by this precession. The maximum inclination reached during the 53-year cycle is about 15 degrees. Therefore, the definition of the geostationary ring foresees a declination range from -15 degrees to +15 degrees.
On the other hand, solar radiation pressure induces an eccentricity that leads to a variation of the orbit radius by ± 75 kilometers in some cases.
This leads to the definition of the geostationary ring as being a segment of space around the geostationary orbit that ranges from 75 km below GEO to 75 km above GEO and from -15 degrees to 15 degrees declination.
