A Method for Determining the Sensor Degradation Rates of NOAA AVHRR Channels 1 and 2

A method is described to determine the degradation rates of NOAA AVHRR visible channels. 38 desert targets (each 20 km×20 km ) were selected over the northwest of China after testing uniformity of the underlying surface. Two cloudfree data sets for the same satellite were sampled from two different periods several years apart. The functional relationships were established between the observed reflectances and the satellite observation angles. By allowing comparison of the functional relationships of the two different periods and computation of the sensor degradation rates using the stepwise regression method, the degradation rates were detemined to be 5.8% and 4.6% per year for channels 1 and 2, respectively, based on the NOAA-9 AVHRR data for October 1985 and September 1988.