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High Earth orbit: geocentric orbits above the altitude of geosynchronous orbit (35,786 km or 22,236 mi). [8] For Earth orbiting satellites below the height of about 800 km, the atmospheric drag is the major orbit perturbing force out of all non-gravitational forces. [11]
A wide variety of sources [5] [6] [7] define LEO in terms of altitude.The altitude of an object in an elliptic orbit can vary significantly along the orbit. Even for circular orbits, the altitude above ground can vary by as much as 30 km (19 mi) (especially for polar orbits) due to the oblateness of Earth's spheroid figure and local topography.
Space debris at geostationary orbits typically has a lower collision speed than at low Earth orbit (LEO) since all GEO satellites orbit in the same plane, altitude and speed; however, the presence of satellites in eccentric orbits allows for collisions at up to 4 km/s (14,400 km/h; 8,900 mph). Although a collision is comparatively unlikely, GEO ...
A geostationary orbit, at 36,000 km (22,000 mi), allows a satellite to hover over a constant spot on the earth since the orbital period at this altitude is 24 hours. This allows uninterrupted coverage of more than 1/3 of the Earth per satellite, so three satellites, spaced 120° apart, can cover the whole Earth.
The Tundra orbit is an eccentric geosynchronous orbit, which allows the satellite to spend most of its time dwelling over one high latitude location. It sits at an inclination of 63.4°, which is a frozen orbit, which reduces the need for stationkeeping. [23] At least two satellites are needed to provide continuous coverage over an area. [24]
Space of high Earth orbits (HEO), between medium Earth orbits (MEO) and the orbit of the Moon. A high Earth orbit is a geocentric orbit with an apogee farther than that of the geosynchronous orbit, which is 35,786 km (22,236 mi) away from Earth. [1] In this article, the non-standard abbreviation of HEO is used for high Earth orbit. [2]
All satellites in MEO have an orbital period of less than 24 hours, with the minimum period (for a circular orbit at the lowest MEO altitude) about 2 hours. [2] Satellites in MEO orbits are perturbed by solar radiation pressure, which is the dominating non-gravitational perturbing force. [3]
The Japanese Space Agency, JAXA, launched its Super Low Altitude Test Satellite, or SLATS (“Tsubame”), in 2017, whose orbit slowly decreased from an initial altitude of 630 km (391 mi) to operate at seven different altitudes, from 271 km (168 mi) to a final altitude of 167.4 km (104.0 mi).