High Earth Orbits
High Earth orbit (HEO) stretches to a level of 35,790 kilometers (22,239 miles) above Earth's surface. When referred to as geostationary orbits, satellites match Earth's rotation, moving in the same direction over the equator. When referred to as geosynchronous orbit, they orbit daily in the same direction as Earth's rotation, but may not remain stationary. Both maintain 24-hour orbital velocities.
Medium Earth Orbits
Medium Earth orbit (MEO) satellite sustain orbital altitudes of 1,200 to 35,792 kilometers (746 to 22,240 miles) above Earth's surface lasting 12 hours per orbit. Satellites in semi-synchronous orbit--used for GPS satellites--maintain a height of 26,560 kilometers (16,504 miles) above Earth's surface.
Low Earth Orbits
Low Earth orbits (LEO) carry orbit levels from 200 to 1200 kilometers (124 to 746 miles) over Earth's surface. Their degree of declination depends on what Earth feature they monitor (rainforests, for example). Sun-synchronous LEOs (polar orbits), circle from the North pole, around the South Pole and back to the North Pole in approximately 99 minutes, crossing specific Earth positions at exactly the same time.