When a satellite is held in orbit, what is it orbiting relative to? What's so special about the orbit of geosynchronous satellites?

Well, you're on to something, Elliott. The Space Satellite Handbook defines a satellite as a small body orbiting a bigger body. So when a satellite is held in orbit, it is orbiting relative to a bigger body. An example is the Moon. Our Moon orbits the Earth. It is smaller than the Earth. So, the Moon would be an example of a satellite that orbits the Earth (the bigger body).

Geosynchronous satellites are man-made satellites that orbit the Earth. They always orbit the Earth at the same altitude (35,785 kilometers). But that's not all that is special about these satellites. These satellites revolve around the Earth at the same speed at which the Earth rotates, or geosynchronous satellites complete one orbit in exactly one day. So a satellite in geosynchronous orbit appears to hover over a single location on Earth.

Scientists can use geosynchronous satellites to map the weather that happens everyday in a region on Earth. These satellites are good at that because they always look at one place on the Earth's surface.

Submitted by Elliott (England)
(September 30, 1997)

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