[Source: NASA Science Missions Directorate: http://nasascience.nasa.gov/missions/smap
The Soil Moisture Active-Passive (SMAP) mission has been recommended by the NRC Earth Science Decadal Survey ... Panel for launch in the 2010-2013 time frame. SMAP will use a combined radiometer and high-resolution radar to measure surface soil moisture and freeze-thaw state, providing for scientific advances and societal benefits. Direct measurements of soil moisture and freeze/thaw state are needed to improve our understanding of regional water cycles, ecosystem productivity, and processes that link the water, energy, and carbon cycles. Soil moisture information at high resolution enables improvements in weather forecasts, flood and drought forecasts, and predictions of agricultural productivity and climate change.
The National Polar-orbiting Operational Environmental Satellite System (NPOESS) Integrated Program Office (IPO) has developed a tri-agency set of requirements for the next generation of polar-orbiting operational environmental satellites. A novel approach combining radar-radiometer and L-band mapping of global soil moisture will allow SMAP to far exceed the NPOESS soil moisture threshold (minimum performance) requirements for sensing depth and spatial resolution. With "fast-track" development, it is possible that SMAP could provide critical gap-filling soil moisture measurements for NPOESS, which were lost when the Conical Microwave Imager/Sounder was cancelled from the first NPOESS platform.