SATELLITE-SENSOR CALIBRATION VERIFICATION WITH THE CLOUD-SHADOW METHOD

An atmospheric-correction method appropriate for high-spatial-resoluti on sensors that uses cloud-shaded pixels together with pixels in a nei ghboring region of similar optical properties is described. This cloud -shadow method uses the difference between the total radiance values o bserved at the sensor for these two regions, thus removing the nearly identical atmospheric radiance contributions to the two signals (e.g., path radiance and Fresnel-reflected skylight). What remains is largel y due to solar photons backscattered from beneath the sea to dominate the residual signal. Normalization by the direct solar irradiance reac hing the sea surface and correction for some second-order effects prov ides the remote-sensing reflectance of the ocean at the location of th e neighbor region, providing a known ground target spectrum for use in testing the calibration of the sensor. A similar approach may be usef ul for land targets if horizontal homogeneity of scene reflectance exi sts about the shadow. Monte Carlo calculations have been used to corre ct for adjacency effects and to estimate the differences in the skylig ht reaching the shadowed and neighbor pixels. (C) 1998 Optical Society of America.