When a satellite is in a geostationary orbit, is it moving at a high speed or not moving at all? How is it able to keep an exact match with earths rotation?

Question

When a satellite is in a geostationary orbit, is it moving at a high speed or not moving at all? How is it able to keep an exact match with earths rotation?

In: Physics

Answer 1

Motion is relative. In Earth’s reference frame, which spins once per day, they are not moving, but that’s not an [inertial reference frame](https://en.wikipedia.org/wiki/Inertial_frame_of_reference). In a non-rotating reference frame, they’re moving about 6700 miles per hour.

The way orbital mechanics works, the lower an orbit is, the faster it is. At the altitude of the International Space Station, it takes aout 90 minutes to go all the way around the world once. At the altitude of the moon, it takes about 27 days. At about 22,000 miles up, the time it takes to go around the Earth is exactly 1 day, which means the satellites at that orbit spin around the Earth at exactly the same rate that the Earth spins around its axis. That’s how satellites at that height always stay above the same spot.