<title>Scan Angle Dependence Of Radiance Recorded By The NOAA-AVHRR</title>

Abstract

NOAA-AVHRR data is being used to monitor global vegetation type and condition and to study various environmental factors in addition to performance of meteorological functions. The AVHRR instrument has ±54° as a maximum scan angle limits and it is necessary to be aware of the effects of sun-target-sensor geometry at extreme scan angles to be able to properly interpret the satellite images. In order to interpret the images for vegetation type and condition analysis it is necessary to calibrate back to the nadir view position. Both simulation studies and empirical investigations with digital scanner data have been performed in order to sufficiently understand the effects of scan angle and sun angle, as well as the effects of atmospheric scattering, to eventually perform adequate calibrations. Not suprisingly, the effects are large and studies are continuing to provide improved calibrations. It is the results of these investigations which we describe in this paper.