Use of Antarctica for validating reflected solar radiation measured by satellite sensors

[1] A technique is presented for validating Sun-normalized radiances measured by polar orbiting sensors over Antarctica in the wavelength range 330–800 nm using model calculations for top of the atmosphere reflectances. An important input to these calculations is a model for the reflective properties of the snow surface, especially its directional nature. Details of this model are presented. Evaluations of the radiance calculations using OMI/Aura, MODIS/Aqua, and MISR/Terra data suggest that the surface representation is the largest source of uncertainty, representing ±1% in radiance at solar zenith angles less than 70°. Radiometric evaluations for limited wavelengths of MODIS, TOMS/Earth Probe, and OMI indicate that the first two are accurate to within the ±2% uncertainties in the technique. The OMI reflectances are lower than predictions by 2.5% to 8%, the smallest difference being near the nadir view and the largest at far off-nadir view angles. A time series of Antarctic 360 nm radiances measured by OMI from launch until 2007 is consistent with no change in sensor response in excess of 1%.