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Low Earth orbit

Orbit around Earth between 160 and 2000 km / From Wikipedia, the free encyclopedia

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A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25.[1] Most of the artificial objects in outer space are in LEO, with an altitude never more than about one-third of the radius of Earth.[2]

Comparison_satellite_navigation_orbits.svg
Orbit size comparison of GPS, GLONASS, Galileo, BeiDou-2, and Iridium constellations, the International Space Station, the Hubble Space Telescope, and geostationary orbit (and its graveyard orbit), with the Van Allen radiation belts and the Earth to scale.[lower-alpha 1]
The Moon's orbit is around 9 times as large as geostationary orbit.[lower-alpha 2] (In the SVG file, hover over an orbit or its label to highlight it; click to load its article.)

The term LEO region is also used for the area of space below an altitude of 2,000 km (1,200 mi) (about one-third of Earth's radius).[3] Objects in orbits that pass through this zone, even if they have an apogee further out or are sub-orbital, are carefully tracked since they present a collision risk to the many LEO satellites.

All crewed space stations to date have been within LEO. From 1968 to 1972, the Apollo program's lunar missions sent humans beyond LEO. Since the end of the Apollo program, no human spaceflights have been beyond LEO.