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 Advan ced Very High Resolution Radiometer (AVHRR) visible channels. Thirty-e ight desert targets (each 20 km X 20 km) were selected over the northw est region of China after testing uniformity of the underlying surface . Two cloud-free datasets for the same satellite were sampled from two different periods several years apart. The functional relationships w ere established between the observed reflectances and the satellite ob servation angles. By allowing comparison of the functional relationshi ps of the two different periods and computation of the sensor degradat ion rates using the stepwise method, the degradation rates were determ ined 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.