High Earth orbit

A high Earth orbit is a geocentric orbit with an apogee farther than that of the geosynchronous orbit, which is 35,786 km (22,236 mi) away from Earth. In this article, the non-standard abbreviation of HEO is used for high Earth orbit.

The development of HEO technology has had a significant impact on space exploration and has paved the way for future missions to deep space. The ability to place satellites in HEO has allowed scientists to make groundbreaking discoveries in astronomy and Earth science, while also enabling global communication and navigation systems.

The Moon's Hill sphere is entered at a distance to the Moon of 60,000 km (37,000 mi), lunar orbits until a distance of 690 km (430 mi) are unstable due to Earth's gravitational reach. Near-rectilinear halo orbits around the Moon are within these distances to the Moon, occupying cislunar space. Earth's hill sphere extends to a distance of 1,471,400 km (914,300 mi), encompassing halo orbits, orbits around the Sun-Earth Lagrange points, with orbits increasingly being heliocentric, co-orbiting with Earth the Sun before orbits go deeper into interplanetary space.