SMAP is one of four first-tier missions recommended by the National Research Council's Committee on Earth Science and Applications from Space (Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond, Space Studies Board, National Academies Press, 2007). SMAP data have both high science value and high applications value. The accuracy, resolution, and global coverage of SMAP soil moisture and freeze/thaw measurements are invaluable across many science and applications disciplines including hydrology, climate, carbon cycle, and the meteorological, environmental and ecology applications communities.

Future water resources are a critical societal impact of climate change, and scientific understanding of how such change may affect water supply and food production is crucial for policy makers. Current climate models uncertainties result in disagreement on whether there will be more or less water regionally compared to today; SMAP data will enable climate models to be brought into agreement on future trends in water resource availability. For these reasons, the Committees Water Resources Panel gave SMAP the highest mission priority within its field of interest.

On Feb 2, 2008, NASA announced that SMAP would be one of two new start missions initiated in FY08. The Earth Science Division (ESD) of the Science Mission Directorate (SMD) at NASA Headquarters determined that SMAP will be implemented as a directed mission within the NASA Earth Systematic Mission (ESM) Program managed by Goddard Space Flight Center (GSFC). The Jet Propulsion Laboratory (JPL) is assigned responsibility for the overall success of the SMAP project.

"...Addressing the environmental challenges will not be possible without increased collaboration between Earth scientists and researchers in other disciplines including the social, behavioral, and economic sciences and policy experts. It is necessary now to build on the paradigm of Earth system science and strengthen its dual role Science and applications. This duality has always been an element of Earth science, but it must be leveraged more effectively than in the past..." (Chapter 1: Earth Science: Scientific Discovery and Societal Applications)

"...The global water cycle describes the circulation of water a vital and dynamic substance in its liquid, solid, and vapor phases as it moves through the atmosphere, the land, and the rivers, lakes, and oceans. Water affects everything animal, vegetable, and mineral on the surface of Earth and in the oceans. Life in its many forms exists because of water, and humans have flourished as a hydraulic civilization. Modern civilization depends on learning how to live within the constraints imposed by the availability of water its excesses and its deficiencies.

"...On a global scale, there are important gaps in knowledge of where water is stored, where it is going, and how fast it is moving. Global measurements from space open a vision for the advancement of water science, or hydrology. This vision includes advances in understanding, data, and information that will improve the ability to manage water and to provide the water-related infrastructure that is needed to provide for human needs and to protect and enhance the natural environment and associated biological systems..." (Chapter 11: Water Resources and the Global Hydrologic Cycle)