GPS Radio Occultation and Mission Results from FORMOSAT-3/COSMIC Spacecraft Constellation

The FORMOSAT-3/COSMIC spacecraft constellation consisting of six LEO satellites is the world's first operational GPS radio occultation mission. The mission is jointly developed by Taiwan's National Space Organization (NSPO) and United States' UCAR in collaboration with NASA's Jet Propulsion Laboratory and Naval Research Laboratory. The FORMOSAT-3/COSMIC mission was successfully launched from Vandenberg on April 15, 2006 into the same orbit plane of the designated 516 km circular parking orbit altitude. All six FORMOSAT-3/COSMIC satellites are maintained in the good state of health and are on their way toward the final constellation of six separate orbit planes with 30-degree separations. Three out of six satellites have reached their final mission orbit of 800 km by the middle of February 2007. The FORMOSAT-3/COSMIC has processed over 2500 good ionospheric sounding profiles and 1800 good atmospheric sounding profiles (-900 mostly above the land mass) per day which has over the number of worldwide radiosondes launched per day. The atmospheric radio soundings data are assimilated into the Numerical Weather Prediction (NWP) models for realtime weather prediction and typhoon/hurricane forecast. This paper describes the mission overview; the space and ground segment architecture; the operations challenges encountered during the constellation deployment phase; and the state-of-the-art achievements and mission results of the FORMOSAT-3/COSMIC that affect the RO data retrievals. The ultimate success of a real-time operation of the FORMOSAT-3/COSMIC mission in the final constellation formation can be anticipated.