The Soil Moisture Active Passive (SMAP) Mission is one of the first-tier Earth observation satellite missions in development by NASA in response to the 2007 National Research Council's Earth Science Decadal Survey. SMAP will allow high-resolution (10 km) and frequent (2-3 days repeat) mapping of near-surface soil moisture and its freeze-thaw state. Soil moisture is a key limiting factor on landsurface exchanges of water and energy with the overlying atmosphere where energy is not limiting (warm season and continental climates). The 10 km resolution requirement is derived from several applications in hydrologic and atmospheric science, which have distinguishing features or significant physical interactions at the hydrometeorological (~10 km) scale. Hydrometeorological phenomena such as convective precipitating systems and atmospheric boundary layer growth over land are affected by spatial variations in surface energy and moisture fluxes. Availability of a hydrometeorological scale soil moisture product allows enhanced insights and possible forecast capabilities of regional weather systems around the world. The freeze/thaw timing is a critical determinant of surface carbon exchange over boreal landscapes and it often determines whether a landscape is a source or sink of carbon. The SMAP mission observatory consists of an L-band radar and radiometer sharing a rotating 6-meter mesh reflector antenna. The antenna is lightweight and deployable from a stowed position. The radar and radiometer instruments will be carried onboard a 3-axis stabilized spacecraft in a 680 km polar orbit with an 8-day repeating (2-3 days revisit and 8 day repeat) ground track. SMAP is taking an aggressive approach to identifying, flagging and mitigating potential anthropogenic radio frequency interference (RFI). These approaches are being incorporated into the radiometer and radar flight hardware and ground processing. Four working groups have been established as a means to enable broad science participation in the SMAP mission (Algorithms, Calibration/Validation, Applications, and Radio-Frequency Interference; see http://smap.jpl.nasa.gov/science/wgroups/). The working groups are led by Science Definition Team (SDT) members and provide forums for information exchange on issues related to SMAP science and applications goals and objectives. SMAP is currently on schedule for launching in late 2014. In this paper the data products and especially the applications plans for SMAP products will be presented. Issues related to algorithm development and pre-launch and post-launch calibration and validation of algorithms will also be outlined. Finally the development and use of and end-to-end global simulator of the mission including dynamic geophysical and simulated instrument measurements subject to noise and orbital considerations will be shown. This simulation environment – the SMAP Algorithm Testbed – is being used for assessing error propagation in the algorithms and for demonstration of SMAP data products impacts on applications.