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The Global Precipitation Measurement (GPM) mission started as an expanded follow-on mission of the Tropical Rainfall
Measuring Mission (TRMM) project to obtain more accurate and frequent observations of precipitation than TRMM. An
important goal for the GPM mission is the frequent measurement of global precipitation using a GPM core satellite and a
constellation of multiple satellites. The GPM core satellite is developed by the US and Japan as like as TRMM, while the
constellation satellites are developed by various countries. The accurate measurement of precipitation will be achieved
by the Dual-frequency Precipitation Radar (DPR) installed on the GPM core satellite. DPR consists of two radars, which
are Ku-band (13.6 GHz) precipitation radar (KuPR) and Ka-band (35.5 GHz) radar (KaPR). KaPR will detect snow and
light rain, and the KuPR will detect heavy rain. In an effective dynamic range in both KaPR and KuPR, drop size
distribution (DSD) information and more accurate rainfall estimates will be provided by a dual-frequency algorithm. The
frequent precipitation measurement every three hours at any place on the globe will be achieved by several constellation
satellites with microwave radiometers (MWRs). JAXA/EORC is responsible for the GPM/DPR algorithm development
for engineering values (Level 1) and physical products (e.g. precipitation estimation) (Level 2 and 3) and the quality
control of the products as the sensor provider. It is also important for us to produce and deliver 3-hourly global
precipitation map in real time in order to make useful for various research and application areas (i.e., the prediction of
the floods). To secure the quality of estimates, the mission must place emphasis on validation of satellite data and
retrieval algorithms.
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