<title>Lunar calibration of geostationary visible-band imagers</title>

Abstract

The U.S. Geological Survey and Northern Arizona University have established a program of lunar photometry with the dedicated Robotic Lunar Observatory (ROLO). This program has the potential to calibrate any past or future visible-band image from a geostationary satellite that contains the moon. As an early application of this technique, a visible-band image of the moon has been obtained from Japan's Geostationary Meteorological Satellite (GMS-5) under viewing and illumination conditions that allow it to be directly compared with a calibrated multi-band image of the moon taken nearly simultaneously from the ground by ROLO. The results demonstrate that the lunar method can potentially calibrate the sensor to an accuracy of a few percent over a wide range of the radiances typical of cloud-free land scenes. However, the inadequate calibration and probable cloud contamination of the particular ground image used preclude an accurate absolute calibration in this case. The merits of this new technique relative to other techniques of calibrating current operational visible-band sensors are discussed and the spectral considerations peculiar to the calibration of broadband sensors are pointed out.