This proposal is to develop analytical cross-calibration techniques for cooperative satellites within a multi-satellite Global Precipitation Mission (GPM) constellation. For GPM, the data from multiple satellite instruments are to be merged into a self-consistent precipitation product, therefore this research is necessary to assure that the instrument radiometric calibrations are likewise made self-consistent. Under the previous Precipitation Measurements Mission science team activities, we have developed a template-based algorithm to search efficiently for coincidences between any pair of satellites with any given time difference. However, when two satellites simultaneously view the same point, generally they have similar, but not identical, observation parameters such as frequency, polarization and view angle. To accommodate these differences, we have developed several candidate algorithms, which predict the ocean brightness temperature observations from one satellite based on the observations of another. Comparison between observed and predicted radiances between two systems can establish cross-calibration consistency. This proposal is to extend the previous results by conducting comprehensive inter-satellite radiometric comparisons between the existing passive microwave imagers TMI, SSMI, SSMIS, AMSR and WindSat. Based upon these studies, we propose to evaluate and refine the current candidate algorithms. Further, we will extend our algorithms to include other natural targets such as tropical rain forest, sea ice and glaciers. Finally, we will investigate the effects of radiometric calibration errors on merged precipitation products.
