Calibration and characterization of the post-launch performance of the visible and near-infrared channels of the Advanced Very High Resolution Radiometer (AVHRR) on board the NOAA-7, -9, and -11 spacecraft

The observed in-orbit degradation in the performance of the visible (channel 1: ≈0.58-0.68 μm) and near-infrared (channel 2: ≈0.72-1.1 μm) channels of the Advanced Very High Resolution Radiometer (AVHRR) on board the NOAA Polar-orbiting Operational Environmental Satellites has been estimated, using vicarious calibrations over the southeastern Libyan desert (21°-23°N; 28°-29°E) which was assumed to be a radiometrically stable calibration target. The annual relative degradation rates, in per cent, for the two channels of the AVHRRs on the NOAA-7, -9, and -11 spacecraft are respectively: 3.6 and 4.3 (NOAA-7); 5.9 and 3.5 (NOAA-9); and 1.2 and 2.0 (NOAA-11). Using the relative degradations, and absolute calibrations of the AVHRR on NOAA-9 spacecraft based on congruent path aircraft/satellite measurements of the upwelling radiance over White Sands, New Mexico (USA), inter-satellite calibration linkages and formulae for the calculation of calibrated radiances/albedos have been developed. The calibrated radiance formulae have been applied to reprocess long-term records of AVHRR-derived geophysical products