Excerpt:

"Although TRMM started as an experimental mission to study tropical rainfall, and was originally expected to last only 3-5 years, it has evolved into the primary satellite in a system of research and operational satellites monitoring precipitation on time scales from 3-hr to inter-annually and beyond. TRMM’s role as the primary satellite in this system is because of the high-quality precipitation information available from its combination of active-passive instruments and the inclined orbit visiting the entire diurnal cycle with frequent intersections with polar-orbiting satellites. Today TRMM data are used to calibrate and integrate precipitation information from multiple polar orbiting satellites/instruments (AMSR on Aqua, SSM/Is on DoD/DMSP and AMSU on NOAA platforms) and geosynchronous satellites into merged precipitation analyses being used both for research and applications. The real-time availability of TRMM products has also resulted in the use of TRMM data by operational weather agencies in the U.S. and around the world for monitoring and forecasting of tropical cyclones, floods and other hazardous weather."