Fire and glint in AVHRR's channel 3: a possible reason for the non-saturation mystery

Abstract
Evidence from a very strong and rare case of sunglint in a NOAA-11 AVHRR image is used to show that a problem exists in the on-board signal processing of channel 3. This problem, associated only with targets of high reflectivity and/or temperature, causes erroneous indication of digital counts (DN) and calculated brightness temperatures for near-saturation ranges in channel 3 images. The explanation proposed, a spurious conversion of the sensor signal to DNs, fits observations of sunglint and fire detection data in AVHRR images of the NOAA-series satellites which could not otherwise be explained.