Continuous, high-resolution measurement of rainfall in the tropics was recently achieved using the Tropical Rainfall Measuring Mission (TRMM) satellite. This satellite was launched from Japan in November 1997 and operated from an altitude of 350 km at an inclination of 35° [Simpson et al., 1996; Kummerow et al., 1998; Kozu and Iguchi, 1999]. The TRMM satellite carries the world's first space-borne Precipitation Radar (PR). The PR is operated at 13.8 GHz with a cross-track scan through nadir and ±17° that results in a 20-km swath width. PR antenna beam-width is 0.71° with 49 observation angle bins within the scanning angle of ±17°.