BRDF STUDY OF GRAY-SCALE SPECTRALON

Satellite instruments operating in the reflective solar wavelength region often require accurate and precise determination of the Bidirectional Reflectance Distribution Function (BRDF) of laboratory based diffusers used in their pre-flight calibrations. In this paper we present gray Spectralon BRDF measured using a monochromatic broadband source at ultraviolet, visible and near-infrared wavelengths. By comparing these results, we quantitatively examine the wavelength and geometrical scatter properties of gray-scale Spectralon. The Spectralon diffusers with specified hemispherical reflectances of 2%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 99% were measured using P and S incident polarized light over a range of incident and scatter angles. The measurements are compared, and the influence of material composition on the BRDF is described. The future application of gray-scale Spectralon in the calibration of spaceborne sensors is described. All data were obtained using the out-of-plane scatterometer located in NASA's Goddard Space Flight Center's Diffuser Calibration Facility. The results are NIST traceable.