high elliptical orbit (satellite comm.) (HEO)
High Elliptical Orbit (HEO) is a highly elliptical satellite orbit, ranging from 500 km to 50,000 km. The closest apsides to Earth are below the orbit of LEO satellites, while the farthest apsides to Earth are above those of GEO satellites.
This extremely elliptical orbit has a long dwell time to the farthest point from Earth and back, which can exceed twelve hours. Whereas the near earth orbit portion is much shorter. Radio communications with HEO satellites can therefore last a very long time before the inclination becomes so great that radio communications can no longer be maintained. HEO satellites are therefore interesting as communications satellites, although the delay times affect the communications of interactive services.