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Encyclopedia > Highly elliptical orbit

Highly Elliptical Orbit (HEO) is an elliptic orbit characterized by a relatively low-altitude perigee and an extremely high-altitude apogee. These extremely elongated orbits can have the advantage of long dwell times at a point in the sky during the approach to and descent from apogee. Visibility near apogee can exceed twelve hours of dwell at apogee with a much shorter and faster-moving perigee phase. Bodies moving through the long apogee dwell can appear still in the sky to the ground when the orbit is at the right inclination, where the angular velocity of the orbit in the equatorial plane matches the rotation of the surface beneath. (For the Earth, this inclination is 63.4 degrees.) This makes these elliptical orbits useful for communications satellites. Two bodies with similar mass orbiting around a common barycenter with elliptic orbits. ... Perigee is the point at which an object in orbit around the Earth makes its closest approach to the Earth. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... MILSTAR:A communication satellite A satellite is any object that orbits another object (which is known as its primary). ...


Examples of HEO orbits offering visibility over Earth's polar regions, which most geosynchronous satellites lack: A geosynchronous orbit is a geocentric orbit that has the same orbital period as the sidereal rotation period of the Earth. ...

  • Molniya orbit, after the former Soviet communications satellite network which used such an orbit.
  • Tundra orbit, also developed for Soviet use.

Much of Russia is at high latitude, so geostationary orbit does not provide full coverage of the region. These Soviet HEO orbits include polar coverage. Molniya orbit is a class of a highly elliptic orbit with inclination of +/-63. ... Tundra orbit is a class of a highly elliptic orbit with inclination of 63. ... It has been suggested that this article or section be merged with geosynchronous orbit. ...


HEO orbits are used by Sirius Satellite Radio. Sirius Satellite Radio NASDAQ: SIRI is one of two satellite radio (DARS) services operating in the United States and Canada. ...


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