A semi-synchronous orbit is an orbit with a period equal to half the average rotational period of the body being orbited, and in the same direction as that body's rotation. For Earth, a semi-synchronous orbit is considered a medium Earth orbit, with a period of just under 12 hours. For circular Earth orbits, the altitude is approximately 20,200 kilometres (12,600 mi). Semi-synchronous orbits are typical for GPS satellites.
See also Molniya orbit List of orbits Synchronous orbit
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