  The validation of NASA Global Precipitation Mission (GPM) satellite
precipitation products is important for their credibility and utility within
the larger community. This document defines GPM ground validation scientific
objectives and several programmatic components for meeting those objectives.
Multi-year, multi-sensor ground-based observation programs in a few locations
are proposed to generate local observation products and global error covariance
products. Focused measurement programs utilizing aircraft, ships, and
ground-based measurements would fill in geographic and scientific gaps not
addressed by the multi-year observing programs.
