Low Earth orbit ||This article needs additional citations for
verification. (May 2012)| A low Earth orbit (LEO) is generally
defined as an orbit below an altitude of approximately 2,000
kilometers (1,200 mi). Given the rapid orbital decay of objects
below approximately 200 kilometers (120 mi), the commonly
accepted definition for LEO is between 160 kilometers (99 mi)
(with a period of about 88 minutes) and 2,000 kilometers (1,200
mi) (with a period of about 127 minutes) above the Earth's
surface. With the exception of the lunar flights of the Apollo
program, all human spaceflights have taken place in LEO (or were
suborbital). The altitude record for a human spaceflight in LEO
was Gemini 11 with an apogee of 1,374.1 kilometers (853.8 mi).
All manned space stations to date, as well as the majority of
artificial satellites, have been in LEO. Orbital characteristics
Objects in LEO encounter atmospheric drag in the form of gases
in the thermosphere (approximately 80–500 km up) or exosphere
(approximately 500 km a