Inter-Satellite Radiometer Calibration of WindSat, TMI and SSMI

NASAs Global Precipitation Measurement (GPM) Mission will consist of a constellation of cooperative satellites with microwave radiometers to make global rainfall measurements. It is crucial that the brightness temperature (T_b) measurements from these satellite radiometers be consistent with each other. This may be achieved by the radiometric inter-comparison of near-simultaneous collocated oceanic measurements from pairs of satellites. In this paper, we describe two methods of performing such inter-comparisons. The first uses a radiative transfer model (RTM) to predict expected Tb differences between a pair of radiometer channels due to frequency and incidence angle differences, and then computes the unexplained relative radiometric bias between the channels over a wide variety of environmental conditions. The other approach uses a multi-variable linear regression built from RTM T_b simulations of all frequency channels for V and H polarizations. These two approaches are used to compare external measurements between the TRMM Microwave Imager (TMI), WindSat (on Coriolis), and SSMI (on DMSP F-13 and F-14).