GPS receive antennas on satellites for precision orbit determination and meteorology

The GPS satellites can be used for extremely precise orbit determination of satellites. This requires carrier phase detection, well known and stable phase characteristics of the antennas and on ground processing. Two antennas for this purpose have been developed by Saab Space, one small for the SWARM project, and a larger general purpose one. The GPS signals are also used for meteorology by the GRAS instrument on MetOp. The phase delays during occultations from a LEO satellite are measured using advanced array antennas.