WHAT KIND OF ORBITS DO SATELLITES HAVE?

A satellite in geostationary orbit takes the same time to orbit the Earth as the Earth does to spin, therefore always remaining over the same point on the planet. This orbit is mainly used for communications satellites. Low-Earth orbits, often used by spy satellites, can be lower than 250km (155 miles) above the planet. Polar-orbit satellites orbit at around 800km (590 miles), while highly-elliptical-orbit satellites have very low altitudes when they are closest to Earth, but pass far beyond the planet when they are at their most distant.

A geosynchronous orbit is a high Earth orbit that allows satellites to match Earth’s rotation. Located at 22,236 miles (35,786 kilometers) above Earth’s equator, this position is a valuable spot for monitoring weather, communications and surveillance. “Because the satellite orbits at the same speed that the Earth is turning, the satellite seems to stay in place over a single longitude, though it may drift north to south,” NASA wrote on its Earth Observatory website.

Satellites are designed to orbit Earth in one of three basic orbits defined by their distance from the planet: low Earth orbit, medium Earth orbit or high Earth orbit. The higher a satellite is above Earth (or any other world for that matter), the slower it moves. This is because of the effect of Earth’s gravity; it pulls more strongly at satellites that are closer to its center than satellites that are farther away. 

So a satellite at low Earth orbit — such as the International Space Station, at roughly 250 miles (400 km) — will move over the surface, seeing different regions at different times of day. Those at medium Earth orbit (between about 2,000 and 35,780 km, or 1,242 and 22,232 miles) move more slowly, allowing for more detailed studies of a region. At geosynchronous orbit, however, the orbital period of the satellite matches the orbit of the Earth (roughly 24 hours), and the satellite appears virtually still over one spot; it stays at the same longitude, but its orbit may be tilted, or inclined, a few degrees north or south.