Assessment of the long-term radiometric calibration stability of the TRMM microwave imager and the WindSat Satellite Radiometers

The NASA´s Global Precipitation Measurement (GPM) mission uses a constellation of international satellites with microwave radiometers, to provide the next-generation of global observations of precipitation. The GPM Intersatellite Calibration Working Group (aka XCAL) has the responsibility to perform the radiometric calibration process to normalize all radiometers to a common source, the GPM Microwave Imager, which serves as a radiometric transfer standard. Prior to the launch of GPM instrument on February 28, 2014, the Tropical Rainfall Measurement Mission (TRMM) Microwave Imager has been used as a proxy for the GMI to develop procedures and data analysis algorithms for inter-comparing two similar, but not identical, radiometers. In this regard, this paper assesses the long-term radiometric calibration stability of TMI relative to WindSat polarimetric radiometer. CFRSL conducted two independent inter-comparisons over oceans in XCAL year (July 2005 - June 2006) and C Y 2011, and results are presented, which demonstrate deciKelvin relative stability over this greater than five-year period.