The Soil Moisture Active/Passive (SMAP) radar

The soil moisture active/passive (SMAP) mission is a NASA mission identified by the NRC ldquodecadal surveyrdquo to measure both soil moisture and freeze/thaw state from space. The mission will use both active radar and passive radiometer instruments at L-band. In order to achieve a wide swath at sufficiently high resolution for both active and passive channels, an instrument architecture that uses a large rotating reflector is employed. The active radar will further utilize SAR processing in order to obtain the sub-footprint resolution necessary for the geophysical retrievals. The SMAP radar has a unique geometry where the antenna footprint is continuously rotated about nadir in a conical fashion, as opposed to the more common side-looking SAR design. In support of the design of the SMAP radar, a point target simulator has been constructed and used to validate the SMAP radar design parameters.