Radiometric calibration of a field transfer radiometer

Abstract

Surface reflectance is one of the key parameters used in automated vicarious calibration. Two ground-viewing radiometers are used to measure the surface reflectance in Dunhuang; however, the radiometers degrade over time. A transfer radiometer is used to determine the trends on site. Before the transfer radiometer is used to correct the ground-viewing radiometer, one should perform an absolute radiometric calibration. Three methods are used to calibrate the transfer radiometer and utilize an intercomparison. The difference between the three methods is small. The uncertainty of each method is analyzed and found to be less than 6% at two standard deviations. Two ground-viewing radiometers are corrected by the transfer radiometer, and the degradation of most channels is less than 5%. The good performance achieved in the field indicates that the three methods are viable for calibrating a field transfer radiometer.