5. Earth orbits

Earth orbits are classified according to their altitude. Low Earth Orbits (LEO, altitude less than 2,000 km) are used for observation of the Earth's surface and telecommunications constellations. Circular medium orbits (MEO, Medium Earth Orbit, altitude around 20,000 km) are used for navigation. High elliptical orbits (HEO, High Earth Orbit, apogee altitude over 50,000 km) are used for space observation.

Earth orbits are based on the WGS84 (World Geodetic System) model:

• Earth's gravitational constant μ _t = 3.986004 × 10 ¹⁴ m ³ · s ^–2 ;

• terrestrial radius equatorial R _e ...