Lunar orbit Lunar orbit In astronomy, lunar orbit (also known as a selenocentric orbit) is the orbit of an object around the Moon. As used in the space program, this refers not to the orbit of the Moon about the Earth, but to orbits by various manned or unmanned spacecraft around the Moon. The altitude at apoapsis (point farthest from the surface) for a lunar orbit is known as apolune, apocynthion, or aposelene, while the periapsis (point closest to the surface) is known as perilune, pericynthion, or periselene, from names or epithets of the moon goddess. Low lunar orbit (LLO)—orbits below altitude—are
Medium Earth orbit Medium Earth orbit Medium Earth orbit (MEO), sometimes called intermediate circular orbit (ICO), is the region of space around Earth above low Earth orbit (altitude of above sea level) and below geostationary orbit (altitude of above sea level). The most common use for satellites in this region is for navigation, communication, and geodetic/space environment science. The most common altitude is approximately ), which yields an orbital period of 12 hours, as used, for example, by the Global Positioning System (GPS). Other satellites in medium Earth orbit include Glonass (with an altitude of ) and Galileo (with an altitude of )