Actually it doesn't have to be geosynchronous, but it couldn't have artificial means of thrust, which satellites don't (except for brief periods for adjustment), and I mixed up geosynchronous with geostationary. Been a long time since that college physics course ...
actually i think as the orbit decays it begins to fall to the earth shortening its orbit length and causing it to increase in speed....
just a thought. no facts to back it up...