A geostationary orbit (or Geostationary Earth Orbit - GEO) is a geosynchronous orbit directly above the Earth's equator (0° latitude), with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero. Geostationary objects appear motionless in the sky, making the GEO an orbit of great interest to operators of communications and weather satellites.

The commonly accepted definition for Low Earth Orbit (LEO) satellites is between 160 - 2,000 km above the Earth's surface. The global telecommunication system "Iridium" requires 66 active satellites in LEO.  These satellites are in six polar low Earth orbital planes at a height of approximately 780 km.

According to Kepler's laws the square of the orbital period of a satellite is directly proportional to the cube of the semi-major axis of its orbit. Elliptic orbit is a Kepler orbit with the eccentricity greater than 0 and less than 1. Example of elliptic orbits is  highly elliptical Molniya orbit with an orbital period of about 12 hours. A satellite placed in a Molniya orbit spends most of its time over a designated area of the earth as a result of "apogee dwell".

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