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Geostationary satellites
Intermediate
Orbit in 24 hours above the equator, appearing fixed in the sky.
Orbit with a 24 h period at about 35,786 km above the equator (r = 42,164 km). It appears fixed in the sky, perfect for TV and weather.
Needs to be above the equator, moving eastward.
Only one altitude fits.
In more detail
A geostationary satellite orbits Earth once per day in the equatorial plane, so it stays above the same point. Its orbital radius is about 42,000 km from Earth's centre.
Real-world uses
- Communications and TV satellites use geostationary orbits.
- Weather satellites monitor the same region continuously from geostationary orbit.
- Weather and television satellites are placed in geostationary orbit so that a ground antenna can point at them without moving.
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Frequently asked questions
Why must it be over the equator?
Because only an equatorial orbit keeps the satellite fixed relative to the ground.
How high is a geostationary satellite?
About 35,786 km above sea level.
Why must a geostationary satellite be above the equator?
Only an equatorial orbit can have the same period as Earth's rotation while staying fixed relative to the ground.
Related topics in Gravitation & Orbits
Orbital velocity · Satellite energy · Orbital period · Polar and low Earth orbits · Weightlessness in orbit · Kepler's first law