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GHRC published the GPM Ground Validation Environment Canada (EC) Precipitation Occurrence Sensor System (POSS) GCPEx guide. The POSS is a bi-static X-band Doppler radar designed by Environment Canada which measures a signal whose frequency is proportional to the particle Doppler velocity and whose amplitude is proportional to the particle scattering cross-section. Its measurements can be used to provide information regarding precipitation occurrence, type, rate, and raindrop size distribution.