Intercalibration of Low Frequency Brightness Temperature Measurements For Long-Term Soil Moisture Record

As part of the development of a long-term soil moisture record, we inter-calibrate several low microwave radiometric sensors (SMOS, SMAP, AMSR-E, AMSR2). We use a radiometric simulator over open ocean as a common reference for sensors operating at various frequencies (L-, C- and X-band) and incidence angles. The simulator includes a radiative transfer model for the Earth's emission and the sensors characteristics. It produces antenna temperatures that can be used to account for differences in the incidence and azimuth angle, timing, and frequency. The double difference method is used to inter-calibrate the various sensors.