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The Global Precipitation Measurement (GPM) mission will provide enhanced space-based precipitation
measurements with sufficient coverage, spatial resolution, temporal sampling, retrieval accuracy, and microphysical
information to advance the understanding of Earth's water and energy cycle and to improve predictions of its
climate, weather, and hydrometeorological processes. Such improvements will in turn improve decision support
systems in broad societal applications (e.g. water resource management, agriculture, transportation, etc). GPM is a
partnership between NASA and the Japan Aerospace Exploration Agency (JAXA), building upon their highly
successful partnership on the Tropical Rainfall Measuring Mission (TRMM). The GPM architecture consists of
NASA satellites operating in partnership with other earth-observing satellites and instruments to produce global
precipitation science data. The current generation of multi-satellite global precipitation products based on
microwave/infrared sensors from uncoordinated satellite missions has for its anchor the TRMM precipitation radar
and the TRMM Microwave Imager measurements over the tropics and subtropics (+/- 35 degrees latitude), with a
mean sampling time of approximately 17 hours. The GPM mission will deploy a spaceborne Core Observatory as a
reference standard to unify a space constellation of research and operational microwave sensors aimed at providing
uniformly calibrated precipitation measurements globally every 2-4 hours. The Core Observatory measurements
will provide, for the first time, quantitative information on precipitation particle size distribution needed for
improving the accuracy of precipitation estimates by microwave radiometers and radars. In addition, the GPM will
also include a second microwave radiometer and a Tracking and Data Relay Satellite (TDRS) communications
subsystem for near real time data relay for a future partner-provided constellation satellite. This second GPM
Microwave Imager (GMI) instrument, flown in a low-inclination orbit, combined with the Core Observatory will
provide an improvement over TRMM in both global coverage and sampling rate (+/- 65 degrees, 10 hour mean
sampling time). GPM is well into its final design and fabrication (Phase C) with planned launches in 2013 and
2014.
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