Semi-synchronous orbit

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 {{convert|20200|km}}.{{cite report | title = NASA Technical Standard 8719.14 (draft) | publisher = NASA Orbital Debris Program Office | date = 8 Aug 2006 | url = http://www.orbitaldebris.jsc.nasa.gov/library/references.html/ | format = PDF | url-status = dead | archiveurl = https://web.archive.org/web/20060823194932/http://www.orbitaldebris.jsc.nasa.gov/library/references.html | archivedate = 2006-08-23 }}{{cite web|title=Catalog of Earth Satellite Orbits|date=6 Sep 2012 | url=http://earthobservatory.nasa.gov/Features/OrbitsCatalog/page2.php}}

Semi-synchronous orbits are typical for GPS satellites.