High Earth orbit

A high Earth orbit is a geocentric orbit with an altitude entirely above that of a geosynchronous orbit (35,786 kilometres (22,236 mi)).[1] The orbital periods of such orbits are greater than 24 hours, therefore satellites in such orbits have an apparent retrograde motion – that is, even if they are in a prograde orbit (90° > inclination ≥ 0°), their orbital velocity is lower than Earth's rotational speed, causing their ground track to move westward on Earth's surface.

This article is about a variation of geocentric orbit. For elliptic orbit, see Highly elliptical orbit.
To-scale diagram of low, medium and high Earth orbits

Examples of satellites in high Earth orbit
Name NSSDC id. Launch date Perigee Apogee Period Inclination
Vela 1A[2][3] 1963-039A 1963-10-17 101,925 km 116,528 km 6,519 min 37.8°
IBEX 2008-051A 2008-10-19 61,941 km 290,906 km 12,963 min 16.9°
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References
  1. "Definitions of geocentric orbits from the Goddard Space Flight Center". User support guide: platforms. NASA Goddard Space Flight Center. Archived from the original on 2010-05-27. Retrieved 2012-07-08.
  2. Vela at Encyclopedia Astronautica
  3. Trajectory Details for Vela 1A from the National Space Science Data Center
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