Orbit types

Various earth orbits to scale; cyan represents low earth orbit, yellow represents medium earth orbit, the black dashed line represents geosynchronous orbit, the green dash-dot line the orbit of Global Positioning System (GPS) satellites, and the red dotted line the orbit of the International Space Station (ISS).

The first satellite, Sputnik 1, was put into orbit around Earth and was therefore in geocentric orbit. By far this is the most common type of orbit with approximately 2456 artificial satellites orbiting the Earth. Geocentric orbits may be further classified by their altitude, inclination and eccentricity.

The commonly used altitude classifications are Low Earth Orbit (LEO), Medium Earth Orbit (MEO) and High Earth Orbit (HEO). Low Earth orbit is any orbit below 2000 km, and Medium Earth Orbit is any orbit higher than that but still below the altitude for geosynchronous orbit at 35786 km. High Earth Orbit is any orbit higher than the altitude for geosynchronous orbit.

Centric classifications

* Galactocentric orbit: An orbit about the center of a galaxy. Earth's sun follows this type of orbit about the galactic center of the Milky Way.
* Heliocentric orbit: An orbit around the Sun. In our 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 planet.
* Geocentric orbit: An orbit around the planet Earth, such as the Moon or artificial satellites. Currently there are approximately 2465 artificial satellites orbiting the Earth.
* Areocentric orbit: An orbit around the planet Mars, such as moons or artificial satellites.

Altitude classifications

* Low Earth Orbit (LEO): Geocentric orbits ranging in altitude from 0–2000 km (0–1240 miles)
* Medium Earth Orbit (MEO): Geocentric orbits ranging in altitude from 2000 km (1240 miles) to just below geosynchronous orbit at 35786 km (22240 miles). Also known as an intermediate circular orbit.
* High Earth Orbit (HEO): Geocentric orbits above the altitude of geosynchronous orbit 35786 km (22240 miles).

Orbital Altitudes of several significant satellites of earth.

Inclination classifications

* Inclined orbit: An orbit whose inclination in reference to the equatorial plane is not zero degrees.
o 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) 90 degrees.
o Polar sun synchronous orbit: A nearly polar orbit that passes the equator at the same local time on every pass. Useful for image taking satellites because shadows will be nearly the same on every pass.

Eccentricity classifications

* Circular orbit: An orbit that has an eccentricity of 0 and whose path traces a circle.
o Hohmann transfer orbit: An orbital maneuver that moves a spacecraft from one circular orbit to another using two engine impulses. This maneuver was named after Walter Hohmann.
* Elliptic orbit: An orbit with an eccentricity greater than 0 and less than 1 whose orbit traces the path of an ellipse.
o Geosynchronous transfer orbit: An elliptic orbit where the perigee is at the altitude of a Low Earth Orbit (LEO) and the apogee at the altitude of a geosynchronous orbit.
o Geostationary transfer orbit: An elliptic orbit where the perigee is at the altitude of a Low Earth Orbit (LEO) and the apogee at the altitude of a geostationary orbit.
o Molniya orbit: A highly elliptic orbit with inclination of 63.4° and orbital period of half of a sidereal day (roughly 12 hours). Such a satellite spends most of its time over a designated area of the planet.
o Tundra orbit: A highly elliptic orbit with inclination of 63.4° and orbital period of one sidereal day (roughly 24 hours). Such a satellite spends most of its time over a designated area of the planet.
* Hyperbolic orbit: An orbit with the eccentricity greater than 1. Such an orbit also has a velocity in excess of the escape velocity and as such, will escape the gravitational pull of the planet and continue to travel infinitely.
* Parabolic orbit: An orbit with the eccentricity equal to 1. Such an orbit also has a velocity equal to the escape velocity and therefore will escape the gravitational pull of the planet and travel until its velocity relative to the planet is 0. If the speed of such an orbit is increased it will become a hyperbolic orbit.
o Escape orbit (EO): A high-speed parabolic orbit where the object has escape velocity and is moving away from the planet.
o Capture orbit: A high-speed parabolic orbit where the object has escape velocity and is moving toward the planet.