Comparison of BRDF results from two different scatterometers for instrument validation in support of satellite instrumentation

Two scatterometers at NASA GSFC Diffuser Calibration Lab (DCL) are used to realize the Bidirectional Reflectance Distribution Function (BRDF) scale transfer from a small NIST traceable BRDF lab standard sample to large-area solar diffuser panels in support of the calibration of remote sensing instruments. The capability of measuring the BRDF of large area solar diffuser panels has been realized by developing a large-area collimated uniform light source and setting the desired fields-of view (FOVs) of instrument detectors. The BRDF measurements for three types of diffuse samples using two different scatterometer measurement equations are compared and consistent results are obtained. The clocking effect of BRDF measured from those diffuse samples is also investigated, and the uncertainty budget of BRDF measurements for the large-area diffuse panel is discussed.