Why is the orbit of satellites at 4 earth radii(22,000 miles) is so special?
1 Answer
Actually about 5 Earth radii. A circular orbit over the Equator has exactly the same period as Earth's own rotation and so remains over one point on Earth.
Explanation:
We call this a geostationary orbit. Satellites in geostationary orbits are used in telecommunications, weather, and environmental studies. By staying over one point on Earth they can establish permanent rather than just periodic communication links with a specific region of the planet.
Geostationary satellites do not last forever. Gravity from the Sun and the Moon, the Earth not being a perfect sphere, and solar radiation all perturb the satellite and make it drift from its intended position. We need to use fuel to correct for this and the sarellite must be remvoed from the skies when the fuel runs out.
Also geostationary satellites cannot study or communicate with the region near the poles because the curvature of Earth blocks communication from the Equator. Alternative orbital paths have been identified to allow polar communication.
For a reference and further reading see here:
