The Soil Moisture Active Passive (SMAP) mission L-Band radar/radiometer instrument

The Soil Moisture Active/Passive (SMAP) mission is a NASA mission identified by the NRC “decadal survey” 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 radiometer uses a more conventional real-aperture resolution, albeit with a significantly larger antenna than flown before. Both the SMAP radar and radiometer must address the effects of radiofrequency interference (RFI).