Statistical Analysis of a Lower Bound on Microwave Radiometer Brightness Temperatures from Space

A novel technique has been developed to verify the absolute accuracy and relative stability of a spaceborne microwave radiometer’s calibration using a statistical analysis of the measured Earth brightness temperatures (TBs). This procedure relies solely on the final, main beam-referenced TBs and so tests the complete end-to-end system calibration, including instrument temperature and non-linearity corrections, the stability of reference TB calibration standards, and far-side lobe antenna pattern corrections. A very stable cold reference TB calibration point results which is known with high absolute accuracy. The data processing steps required to produce the cold reference TB are described here. The technique has been tested previously at a nadir viewing angle of incidence. Its application, at oblique angles, to both conical and cross-track scanning imagers is considered here.