Highly-Elliptical Orbit

The third orbit used by communications satellites is a highly-elliptical orbit, or "HEO.' Satellites in HEO have orbits that are close to the Earth at one point of their orbit, but are much farther away from the Earth at other times.

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Remember how we said that a satellite moves faster closer to the Earth than it does farther away from the Earth? Because of this fact, the satellite appears to slow down as it moves away from the Earth and speeds up as it approaches the Earth. Thus, for a while the satellite appears nearly stationary in the sky while it is farthest away from the Earth. For this reason, HEO satellites imitate GEO satellites in that it is not necessary to re-point an antenna constantly while communicating to track the satellite across the sky.

Often highly-elliptical orbits are used to serve areas to the far north or south of the Earth, which cannot be reached using geostationary satellites. Because Russia has a lot of land that is far to the north, the use of highly-elliptical orbits was pioneered by the Russians.