Improved absolute radiometric calibration of a UHF airborne radar

The AirMOSS airborne SAR operates at UHF and produces fully polarimetric imagery [1]. The AirMOSS radar data are used to produce Root Zone Soil Moisture (RZSM) depth profiles. The absolute radiometric accuracy of the imagery, ideally of better than 0.5 dB, is key to retrieving RZSM, especially in wet soils where the backscatter as a function of soil moisture function tends to flatten out [2]. In this paper we assess the absolute radiometric uncertainty in previously delivered data, describe a method to utilize Built In Test (BIT) data to improve the radiometric calibration, and evaluate the improvement from applying the method.