Advantages of Calibration Attitude Maneuvers for spaceborne microwave radiometer missions

Earth observing satellite microwave radiometers have been in use since the 1960's providing geoscientists invaluable insight into the complex interaction of the atmosphere, ocean and land in the climate of our planet. Such key instruments must be vetted of any calibration issues so as to provide the utmost accurate and stabilized dataset for scientific analysis. There are several post-launch radiometric calibration methods currently in use, and most require multiple ancillary data sets and a lengthy duration (typically one year) of on-orbit brightness temperature observations to obtain conclusive results. However, one on-orbit calibration method that can provide accurate and early results is the Calibration Attitude Maneuver (CAM), which encompasses Deep Space Calibration (DSC) and a new use of the near-Nadir Second Stokes (SS) analysis. This paper provides examples of CAMs that have aided in the calibration of the Tropical Rainfall Measuring Mission Microwave Imager (TMI) and the Global Precipitation Measurement Microwave Imager (GMI). Excellent results obtained suggest the use of the CAM as a recommended tool for on-orbit calibration for microwave radiometers.