Tropical Rainfall Measurement Mission (TRMM) is a satellite that observes precipitation distribution from 403 km above the earth with the orbital inclination at 35 degrees. TRMM has five instruments, which are Precipitation Radar (PR), TRMM Microwave Imager (TMI), Visible Infrared Scanner (VIRS), Clouds and the Earth's Radiant Energy System (CERES), and Lighting Imaging Sensor (LIS). Among the three primary instruments on TRMM, the most innovative is PR. Other instruments similar to the TMI and the VIRS have operated in space before [4]. TMI is similar to Special Sensor Microwave/Imager (SSM/I) [Simpson et al., 1996 on 2], while infrared sensors on geostationary platforms for tracking cloud movement has been introduced in 1970’s [3].
