FORMOSAT-3/COSMIC

FORMOSAT-3/COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate), also known as COSMIC-1, was the first GPS radio occultation constellation, operated jointly by UCAR (USA) and Taiwan's National Space Organization (NSPO), with NOAA, JPL, the US Naval Research Laboratory, and the US Air Force as programme partners.^[1][2] Six microsatellites launched together on 14 April 2006 and were gradually deployed into six orbital planes at 800 km altitude and 72 degrees inclination, providing near-uniform global coverage for GNSS radio occultation profiling.^[1]

Each satellite carried the IGOR dual-frequency GPS receiver (Broad Reach Engineering, based on JPL technology) for atmospheric and ionospheric radio occultation, a TIP ultraviolet airglow photometer for ionospheric electron density profiling, and a CERTO/TBB radio beacon for ionospheric tomography.^[1] The constellation delivered temperature, humidity, and pressure profiles through the neutral atmosphere as well as electron density profiles in the ionosphere, amassing over ten million profiles by 2016.^[2]

COSMIC-1 demonstrated that a constellation of low-cost microsatellites could produce operationally useful atmospheric profiles at global scale, and its data were directly assimilated by national weather prediction centres, establishing GNSS radio occultation as an operational NWP input.^[3] Designed for a five-year mission, the constellation operated for fourteen years; NOAA and UCAR officially decommissioned it on 1 May 2020.^[3] It was succeeded by FORMOSAT-7/COSMIC-2, launched in 2019 with expanded low-latitude coverage and multi-constellation reception.^[4]