GPM measures precipitation globally; over the land and ocean, in both the tropics, mid-latitudes, and cold locations near the poles over a latitude band of 65ºN-65ºS. GPM measures both light, heavy, and frozen precipitation including the microphysical properties of precipitation particles. This wide range of locations and precipitation types presents a host of challenges not encountered by TRMM, which only measured moderate to heavy rainfall in the tropics.