AIRBORNE IMAGING MICROWAVE RADIOMETER .1. RADIOMETRIC ANALYSIS

The airborne imaging microwave radiometer (AIMR) was designed and buil t for regional scale sea ice mapping. It operates at 37 and 90 GHz (no minal), and collects radiance at two orthogonal polarizations from whi ch we can compute horizontal and vertical polarizations. The sensitivi ty or precision (Delta T) of the radiometric data is on the order of 0 .5-0.8 K for the 37 GHz channels and 0.8-1.5 for the 90 GHz channels. A detailed error analysis was conducted to assess the accuracy of the radiometric measurements. The error in the brightness temperatures of the original orthogonal polarizations channels was found to be on the order of 0.35-0.45 K for the 37 GHz channel and 0.55-0.65 K for the 90 GHz channel. The polarization conversion introduces additional errors and these are analyzed and computed for the LIMEX-89 data. The total error due to both calibration and polarization conversion for incidenc e angles greater than 20 degrees is on the order of 0.65-0.70 K for 37 GHz and 0.75-0.85 K for 90 GHz. For incidence angles between 10 degre es and 20 degrees the error can be up to 1.5 K. As the incidence angle approaches zero the distinction between horizontal and vertical polar ization breaks down and the error approaches infinity.