The first satellite, Sputnik 1, was put into orbit around World and was therefore in geocentric orbit. By far this is the most common range of orbit with roughly 2456 man made satellites revolving about the World. Geocentric orbits may be further categorized by their elevation, tendency and eccentricity.The widely used elevation categories are Low Earth orbit (LEO), Medium Earth Orbit (MEO) and Higher Earth Orbit (HEO). Low World orbit is any orbit below 2000 km, and Method World orbit is any orbit greater than that but still below the elevation for geosynchronous orbit at 35786 km. Great World orbit is any orbit greater than the elevation for geosynchronous orbit.
Centric classifications
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.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.
Areocentric orbit: An orbit around the planet Mars, such as by moons or artificial satellites.
The general structure of a satellite is that it is connected to the earth stations that are present on the ground and
connected through terrestrial links.
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 2,000 km (1,200 mi) to just below geosynchronous orbit at 35,786 km (22,236 mi). Also known as an intermediate circular orbit.
High Earth orbit (HEO): Geocentric orbits above the altitude of geosynchronous orbit 35,786 km
(22,236 mi).
Inclination classifications
Inclined orbit: An orbit whose inclination in reference to the
equatorial plane is not zero degrees.
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.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.
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.
