COSMIC (FORMOSAT-3)

GPS radio occultation measures how GPS signals bend as they pass through Earth's atmosphere, allowing scientists to derive temperature, pressure, and humidity profiles from the surface up to about 40 km altitude. The six COSMIC satellites receive signals from rising and setting GPS satellites through the atmosphere, producing approximately 2,000-2,500 vertical atmospheric profiles per day. This data is particularly valuable because it provides consistent, all-weather measurements that improve weather forecasting models.

FORMOSAT-3/COSMIC was a joint mission between Taiwan's National Space Organization (NSPO) and the United States, primarily through NOAA, NSF, and the U.S. Air Force. Taiwan contributed the satellite bus and launch, while American agencies provided the GPS occultation science instruments and ground systems. The collaboration established a model for international weather satellite partnerships that continued with the follow-on FORMOSAT-7/COSMIC-2 mission launched in 2019.

The successor mission, FORMOSAT-7/COSMIC-2, was launched in June 2019 on a SpaceX Falcon Heavy rocket, deploying six satellites into low-inclination orbits. COSMIC-2 provides significantly more atmospheric soundings than its predecessor and focuses on tropical regions where weather observations are sparse. The mission continues the Taiwan-U.S. partnership and represents a major upgrade in radio occultation capability.

COSMIC data was rapidly assimilated into operational forecasting systems at agencies like NOAA, ECMWF, and the UK Met Office, demonstrably improving forecast accuracy particularly for hurricane tracks and polar regions. The satellite constellation provided approximately 2,500 atmospheric profiles daily with near-uniform global coverage. Studies showed that COSMIC radio occultation data improved 5-day forecast accuracy by an amount comparable to adding other major observing systems.