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A satellite orbit.

A satellite orbit.


An orbit is the path a body takes around object or point in space under the influence of various physical forces, including gravity in its periodic revolution. The term is used to describe both natural paths, such as the Earth around the Sun, and artificial paths, such as a spacecraft around the Earth. Earth satellite orbits with inclinations near 0 degree are called equatorial orbits because the satellite stays nearly over the equator. Orbits with inclinations near 90 degrees are called polar orbits because the satellite crosses over (or nearly over) the north and south poles.

The distance the satellite travels above the Earth also describes orbits. A low-Earth-orbit flies at a distance starting at an altitude of about 100 miles (161 kilometers). A medium earth orbit (MEO) satellite is one with an orbit within the range from several hundred miles to a few thousand miles above the earth's surface. A geosynchronous orbit or geostationary orbit travels 22,300 miles above the Earth.

Orbits are elliptical rather than perfectly circular. The closest point of an orbit to the Earth is its perigee. The most distant point is its apogee. The line connecting the apogee and the perigee is called the line-of-apsides.

The orbital plane can be pictured as a flat circular plane containing the satellite's orbit that passes through the center of the Earth.