MSS

A constellation (i.e., system) of satellites placed at altitudes and in orbits such that they move around the Earth at a different speed than the Earth rotates on its axis and, therefore, appear to be in motion.The MSS classification includes LEO (Low Earth Orbit) and MEO (Middle Earth Orbit) systems. An MSS is in contrast to an FSS (Fixed Satellite System), in which the satellites appear to be fixed in space due to their positioning in geosynchronous Earth orbit (GEO). See also FSS, GEO, LEO, MEO, and satellite.