Low Earth orbit

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 (or about 2000 kilometers).^[2]

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.

No human spaceflights other than the lunar missions of the Apollo program have taken place beyond LEO. All crewed space stations to date have operated within LEO.

^ "Current Catalog Files". Archived from the original on 26 June 2018. Retrieved 13 July 2018. LEO: Mean Motion > 11.25 & Eccentricity < 0.25
^ Sampaio, Jarbas; Wnuk, Edwin; Vilhena de Moraes, Rodolpho; Fernandes, Sandro (1 January 2014). "Resonant Orbital Dynamics in LEO Region: Space Debris in Focus". Mathematical Problems in Engineering. 2014: Figure 1: Histogram of the mean motion of the cataloged objects. doi:10.1155/2014/929810. Archived from the original on 1 October 2021. Retrieved 13 July 2018.
^ "IADC Space Debris Mitigation Guidelines" (PDF). INTER-AGENCY SPACE DEBRIS COORDINATION COMMITTEE: Issued by Steering Group and Working Group 4. September 2007. Archived (PDF) from the original on 17 July 2018. Retrieved 17 July 2018. Region A, Low Earth Orbit (or LEO) Region – spherical region that extends from the Earth's surface up to an altitude (Z) of 2,000 km

[1] "Current Catalog Files". Archived from the original on 26 June 2018. Retrieved 13 July 2018. LEO: Mean Motion > 11.25 & Eccentricity < 0.25

[2] Sampaio, Jarbas; Wnuk, Edwin; Vilhena de Moraes, Rodolpho; Fernandes, Sandro (1 January 2014). "Resonant Orbital Dynamics in LEO Region: Space Debris in Focus". Mathematical Problems in Engineering. 2014: Figure 1: Histogram of the mean motion of the cataloged objects. doi:10.1155/2014/929810. Archived from the original on 1 October 2021. Retrieved 13 July 2018.

[UNOOSA-3] "IADC Space Debris Mitigation Guidelines" (PDF). INTER-AGENCY SPACE DEBRIS COORDINATION COMMITTEE: Issued by Steering Group and Working Group 4. September 2007. Archived (PDF) from the original on 17 July 2018. Retrieved 17 July 2018. Region A, Low Earth Orbit (or LEO) Region – spherical region that extends from the Earth's surface up to an altitude (Z) of 2,000 km

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