The orbital period of the majority of the satellites in our sky is much shorter than 24 hours. They “rotate” faster than the Earth so from Earth they appear to race eastward across the sky. The Moon has an orbital period of about 28 days. It cannot keep up with the Earth’s rotation and so from Earth is seen to move westward in the night sky. A satellite in the geostationary orbit shares the same axis and rate of rotation as the Earth. As such, from Earth, it appears to be fixed at the same spot in the sky. Cool.
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Why must the GEO orbit be equatorial? This video explains.
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Why must GEO satellites be parked at the high (and thus expensive) altitude of 36,000 km? This video explains.
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So do you know how to calculate the GEO altitude? This video explains.
