1. Introduction
The Soil Moisture Active Passive (SMAP) is an Earth-orbiting satellite mission that will collect high-accuracy and high-resolution soil moisture and freeze/thaw measurements over Earth's land masses. This data will be invaluable to understanding current and future water resources, providing input to multiple disciplines, including: climatology, hydrology, meteorology, ecology, and carbon cycle studies. The data will improve the accuracy of weather and climate models and thereby aid in the prediction of natural disasters such as droughts and floods. The mission science requires viewing the same locations on the Earth regularly to track changes in soil moisture and freeze/thaw conditions; therefore, global science data will be collected every three days.