TRMM

TRMM, short for Tropical Rainfall Measuring Mission, was a joint mission of NASA and the Japan Aerospace Exploration Agency (JAXA) designed to monitor tropical rainfall and the structure of convective clouds. Launched in 1997, the satellite operated in a near-equatorial low Earth orbit for about 17 years, collecting precipitation data to improve understanding of the global water cycle and to support weather and climate research.

Its instrument payload combined active and passive sensing: the Precipitation Radar (PR) provided vertical rainfall profiles; the TRMM Microwave Imager (TMI) measured radiance across multiple microwave channels to estimate rainfall rates; the Visible and Infrared Scanner (VIRS) observed cloud cover and cloud-top temperatures; the Lightning Imaging Sensor (LIS) detected optical flashes from storms.

TRMM produced the first high-resolution, spaceborne rain measurements over the tropics and subtropics, allowing detailed studies of rainfall structure, diurnal cycles, and extreme events. The data improved rainfall retrieval algorithms, aided data assimilation in weather and climate models, and helped calibrate and validate other satellite precipitation sensors.

By laying the groundwork for global precipitation monitoring, TRMM directly influenced the development of the Global Precipitation Measurement (GPM) mission and the network of partner satellites that followed. Its data archives remain publicly available and continue to support climatological analyses and hydrological research.

TRMM was retired in 2015 after more than a decade of operation; its legacy endures in the ongoing use of its rainfall datasets and in the design of subsequent precipitation missions.