Correction method of physical temperature variation for airborne double-antenna microwave radiometer

In this paper, the principle of the Ka-band airborne double-antenna microwave radiometer (ADAMR) based on the autogain compensative and noise coupling techniques is reviewed firstly. The radiometer has been applied successfully to detect the atmospheric supercooled water content. Although the auto-gain compensative technique can compensate the gain fluctuation to keep the radiometer's stability by measuring the output variation of reference noise source, it also introduces measurement error caused by the physical temperature change of the reference noise source. For this reason, a temperature correction method for the output voltage of this radiometer is proposed. The corrected equations are derived by using the regression relationship between the measurement error and the physical temperature of the reference noise source. In order to demonstrate the feasibility of this method, the outdoor contrast experiment was carried out. For the 30° antenna channel, the RMSE of the two-point calibration method is 2.039K while the RMSE of the correction method is 0.718K. For the 90° antenna channel, the RMSE of the two-point calibration method is 2.113K while the RMSE of the correction method is 0.448K. The results prove that the correction method can effectively correct the output of the radiometers with the auto-gain compensative technique.