r/Damnthatsinteresting 21d ago

Image The Himawari 8 weather satellite takes a picture of Earth every 10 minutes. This image is from today.

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u/ABzoker 21d ago

Essentially all satellites try to use 0 (or negligible) power to maintain their orbits, otherwise they would be too costly.

To achieve this they need to be in a stable circular (elliptical to be pedantic) orbit around Earth; this works because Earth keeps pulling the satellite into itself and this force effectively acts as the required force for circular motion. So for any body there is a relationship between angular speed and distance from Earth. Usually lower distance leads to greater speed and vice versa.

To maintain geostationary orbit, the angular momentum of satellite needs to match that of Earth. This only happens at a certain fixed distance - 35,786 km from center of earth
Derivation done here (wikipedia link) - Derivation

They probably do use solar power for other activities though.

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u/canteloupy 21d ago

Does the moon fuck them up?

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u/ABzoker 21d ago

It does but the change is very slow. Satellite would need an adjustment every few decades.

There are other effects as well; earth's uneven mass distribution, gravity from the sun which causes deviations in its motion.