Estimation of TRMM microwave imager antenna temperature during Deep Space Calibration maneuvers

In 1998, the Tropical Rainfall Measuring Mission observatory performed a set of maneuvers known as Deep Space Calibration (DSC) that allowed the TRMM Microwave Imager conically scanning antenna beam to view a known non-polarized calibration scene of 2.7 Kelvin. However, during this period the radiometric transfer function (radiometric counts-to-T_A) was only valid for only a very short portion of main reflector deep space view. This paper discusses three methods of reconstructing the radiometric transfer function thereby providing a longer time series of Antenna Temperature (T_A) for absolute calibration. Earth emission entering into the feed spillover region of the antenna pattern is acknowledged within this paper. The motivation of this work is for preparation of the Global Precipitation Measurement (GPM) Microwave Imager (GMI) DSC maneuvers set for May of 2014.