Low Earth Orbit
A low Earth orbit (LEO) is an orbit around Earth characterized by a period of 128 minutes or less—resulting in at least 11.25 orbits per day—and an eccentricity of less than 0.25.
The LEO region is defined as the area of space below an altitude of 2,000 kilometers (1,200 mi), which is approximately one-third of the Earth’s radius. Most artificial objects in outer space are located within this orbit, with a peak concentration at an altitude of around 800 km (500 mi). The upper limit of LEO, before transitioning into medium Earth orbit (MEO), is situated at 2,000 kilometers, near the beginning of the inner Van Allen radiation belt.
Because of the high concentration of satellites in this zone, objects passing through it are carefully tracked. This includes even those with an apogee further out or sub-orbital trajectories, as they present a significant collision risk to the numerous satellites operating within LEO.
As of 2026, all space stations operate in geocentric orbits within the LEO zone. The only human spaceflights to venture beyond LEO were the lunar missions of the Apollo program from 1968 to 1972 and the Artemis II lunar flyby scheduled for 2026.
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