A method is described to determine the degradation rates of NOAA Advanced Very High Resolution Radiometer (AVHRR) visible channels. Thirty-eight desert targets (each 20 km × 20 km) were selected over the northwest 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 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 method, the degradation rates were determined 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.

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