HEO (highly elliptical orbit)
A highly elliptical orbit (HEO) is a stretched, egg-shaped orbit with a low perigee and a very high apogee, letting a satellite linger for hours over one hemisphere.
Classic examples are Russia's Molniya and Tundra orbits, which dwell over high latitudes that geostationary satellites can barely reach.
Because the satellite moves slowly near apogee and quickly near perigee, most of its time is spent high above the target region.
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Related terms
- Apogee — Apogee is the point in an orbit around Earth where the satellite is farthest from the planet.
- Perigee — Perigee is the point in an orbit around Earth where the satellite is closest to the planet.
- Orbital period — The orbital period is the time a satellite takes to complete one full orbit, set almost entirely by its altitude.
