FIRE AND GLINT IN AVHRRS CHANNEL 3 - A POSSIBLE REASON FOR THE NONSATURATION MYSTERY

Evidence from a very strong and rare case of sunglint in a NOAA-11 AVH RR 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-sa turation ranges in channel 3 images. The explanation proposed, a spuri ous conversion of the sensor signal to DNs, fits observations of sungl int and fire detection data in AVHRR images of the NOAA-series satelli tes which could not otherwise be explained.