Formosat3

Formosat-3, also known as FORMOSAT-3 or FORMOSAT-3/COSMIC, is a satellite mission developed through a collaboration between Taiwan's National Space Organization (NSPO) and United States agencies including NOAA, with support from NASA and UCAR. Its central objective is to improve weather forecasting and atmospheric science by collecting data via GPS radio occultation (RO). The constellation comprises six small satellites placed in low Earth orbit in near-polar, sun-synchronous trajectories at roughly 800 kilometers altitude. Each satellite carries a GPS RO instrument that analyzes GPS signals as they pass through Earth's atmosphere, enabling the retrieval of vertical profiles of temperature, pressure, and humidity from near the surface to the upper troposphere.

Initiated in the 2000s, Formosat-3 was launched in two batches during the late 2000s. The data produced by the constellation became a core component of the international COSMIC project, providing extensive RO measurements used by meteorological agencies and researchers worldwide to improve the assimilation of sensory data into numerical weather prediction models. The mission demonstrated the value of international collaboration and the use of small satellite constellations for atmospheric sounding.

Formosat-3's data legacy helped pave the way for subsequent initiatives, including COSMIC-2, which expanded the RO capability with more satellites and broader collaboration. The Formosat-3 program is often cited as a landmark example of cross-border scientific cooperation and a practical contributor to operational meteorology.