Common abbreviations
List of abbreviations of common Earth orbits
List of abbreviations of other orbits
Classifications
The following is a list of types of orbits:
Centric classifications
Galactocentric orbit: An orbit about the center of a galaxy. The Sun follows this type of orbit about the Galactic Center of the Milky Way. Heliocentric orbit: An orbit around the Sun. In the Solar System, all planets, comets, and asteroids are in such orbits, as are many artificial satellites and pieces of space debris. Moons by contrast are not in a heliocentric orbit but rather orbit their parent object. Geocentric orbit: An orbit around the planet Earth, such as that of the Moon or of artificial satellites. Selenocentric orbit (named after Selene): An orbit around Earth's Moon. Areocentric orbit (named after Ares): An orbit around the planet Mars, such as that of its moons or artificial satellites.
For orbits centered about planets other than Earth and Mars and for the dwarf planet Pluto, the orbit names incorporating Greek terminology is less commonly used Mercury orbit (Hermeocentric orbit, named after Hermes): An orbit around the planet Mercury. Venus orbit (Cytherocentric orbit, named after Cythera): An orbit around the planet Venus. Jupiter orbit (Zenocentric orbit, named after Zeus, or Latin equivalent Jovicentric): An orbit around the planet Jupiter. Saturn orbit (Cronocentric orbit, named after Cronus, or Latin equivalent Saturnicentric): An orbit around the planet Saturn. Uranus orbit (Uranocentric orbit, named after Uranus): An orbit around the planet Uranus. Neptune orbit (Poseidocentric orbit, named after Poseidon): An orbit around the planet Neptune. Pluto orbit (Hadeocentric orbit, named after Hades): An orbit around the dwarf planet Pluto.
Altitude classifications for geocentric orbits
Very Low Earth Orbit (VLEO) is defined as altitudes between approximately 100 - 450 km above Earth’s surface. Low Earth orbit (LEO): geocentric orbits with altitudes below . Medium Earth orbit (MEO): geocentric orbits ranging in altitude from to just below geosynchronous orbit at . Also known as an intermediate circular orbit. These are used for Global Navigation Satellite System spacecraft, such as GPS, GLONASS, Galileo, BeiDou. GPS satellites orbit at an altitude of with an orbital period of almost 12 hours. Geosynchronous orbit (GSO) and geostationary orbit (GEO) are orbits around Earth matching Earth's sidereal rotation period. Although terms are often used interchangeably, technically a geosynchronous orbit matches the Earth's rotational period, but the definition does not require it to have zero orbital inclination to the equator, and thus is not stationary above a given point on the equator, but may oscillate north and south during the course of a day. Thus, a geostationary orbit is defined as a geosynchronous orbit at zero inclination. Geosynchronous (and geostationary) orbits have a semi-major axis of . This works out to an altitude of . Both complete one full orbit of Earth per sidereal day (relative to the stars, not the Sun). High Earth orbit: geocentric orbits above the altitude of geosynchronous orbit ().
For Earth orbiting satellites below the height of about 800 km, the atmospheric drag is the major orbit perturbing force out of all non-gravitational forces. Above 800 km, solar radiation pressure causes the largest orbital perturbations. However, the atmospheric drag strongly depends on the density of the upper atmosphere, which is related to the solar activity, therefore the height at which the impact of the atmospheric drag is similar to solar radiation pressure varies depending on the phase of the solar cycle.
Inclination classifications
Inclined orbit: An orbit whose inclination in reference to the equatorial plane is not 0. Polar orbit: An orbit that passes above or nearly above both poles of the planet on each revolution. Therefore, it has an inclination of (or very close to) either 90 degrees or −90 degrees. Polar Sun-synchronous orbit (SSO): A nearly polar orbit that passes the equator at the same local solar time on every pass. Useful for image-taking satellites because shadows will be the same on every pass. Non-inclined orbit: An orbit whose inclination is equal to zero with respect to some plane of reference. Ecliptic orbit: A non-inclined orbit with respect to the ecliptic. Equatorial orbit: A non-inclined orbit with respect to the equator. Near equatorial orbit: An orbit whose inclination with respect to the equatorial plane is nearly zero. This orbit allows for rapid revisit times (for a single orbiting spacecraft) of near equatorial ground sites.