Low Earth orbit

[1] Most of the artificial objects in outer space are in LEO, peaking in number at an altitude around 800 km (500 mi),[2] while the farthest in LEO, before medium Earth orbit (MEO), have an altitude of 2,000 kilometers, about one-third of the radius of Earth and near the beginning of the inner Van Allen radiation belt.

The term LEO region is 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.

While definitions based on altitude are inherently ambiguous, most of them fall within the range specified by an orbit period of 128 minutes because, according to Kepler's third law, this corresponds to a semi-major axis of 8,413 km (5,228 mi).

Objects in LEO orbit Earth between the denser part of the atmosphere and below the inner Van Allen radiation belt.

Satellites in orbits that reach altitudes below 300 km (190 mi) decay quickly due to atmospheric drag.

Some communication satellites use much higher geostationary orbits and move at the same angular velocity as the Earth as to appear stationary above one location on the planet.

The effects of adding such quantities of vaporized metals to Earth's stratosphere are potentially of concern but currently unknown.

[18] This has caused growing concern in recent years, since collisions at orbital velocities can be dangerous or deadly.

This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.