Demonstration of a Combined Active/Passive L-Band Microwave Remote Sensing Airborne Instrument

The Passive Active L-Band System (PALS) is an airborne microwave instrument suite that combines a separate radar and radiometer airborne instrument with a common antenna. PALS has been used for salinity, wind speed, and soil moisture measurements, which is critical for calibration and validation of the Soil Moisture Active Passive (SMAP) satellite brightness temperature measurements. The combined 1.413 GHz radiometer and 1.26 GHz radar measurements can provide high-accuracy soil moisture measurements over vegetated areas. The new upgraded version of the PALS instrument employs a novel single-chain receiver topology and combines the radar and radiometer instrument. The reduced-noise single-chain receiver PALS instrument was deployed on a DC-3 aircraft for soil moisture measurement in the summer of 2019. Index Terms— Airborne, Radar, Radiometer, RFI, Receivers, Balanced Amplifier, Soil Moisture.