Laboratory-based bidirectional reflectance distribution functions of radiometric tarps.

Abstract

Laboratory-based bidirectional reflectance distribution functions (BRDFs) of radiometric tarp samples used in the vicarious calibration of Earth remote sensing satellite instruments are presented in this paper. The results illustrate the BRDF dependence on the orientation of the tarps’ weft and warp threads. The study was performed using the GSFC scatterometer at incident zenith angles of $0°$, $10°$, and $30°$; scatter zenith angles from $0°$ to $60°$; and scatter azimuth angles of $0°$, $45°$, $90°$, $135°$, and $180°$. The wavelengths were $485\mathrm{nm}$, $550\mathrm{nm}$, $633\mathrm{nm}$, and $800\mathrm{nm}$. The tarp’s weft and warp dependence on BRDF is well defined at all measurement geometries and wavelengths. The BRDF difference can be as high as 8% at $0°$ incident angle and 12% at $30°$ incident angle. The fitted BRDF data show a very small discrepancy from the measured ones. New data on the forward and backscatter properties of radiometric tarps are reported. The backward scatter is well pronounced for the white samples. The black sample has well-pronounced forward scatter. The provided BRDF characterization of radiometric tarps is an excellent reference for anyone interested in using tarps for radiometric calibrations. The results are NIST traceable.