Long-term calibration monitoring of the bidirectional reflectance distribution function (BRDF) of Spectralon diffusers in the air-ultraviolet is presented. Four Spectralon diffusers were monitored in this study. Three of the diffusers, designated as H1, H2, and H3, were used in the prelaunch radiance calibration of the Solar Backscatter Ultraviolet/2 (SBUV/2) satellite instruments on National Oceanic and Atmospheric Administration (NOAA) 14 and 16. A fourth diffuser, designated as the 400 diffuser, was used in the prelaunch calibration of the Ozone Mapping and Profiler Suite (OMPS) instrument scheduled for initial flight in 2009 on the National Polar Orbiting Environmental Satellite System Preparatory Project. The BRDF data of this study were obtained between 1994 and 2005 using the scatterometer located in the National Aeronautics and Space Administration Goddard Space Flight Center Diffuser Calibration Laboratory. The diffusers were measured at 13 wavelengths between 230 and 425 nm at the incident and scatter angles used in the prelaunch calibrations of SBUV/2 and OMPS. Spectral features in the BRDF of Spectralon are also discussed. The comparison shows how the air-ultraviolet BRDF of these Spectralon samples changed over time under clean room deployment conditions.
We demonstrate a general feature of organic films between a substrate and a deformable cladding layer: the capability of forming periodic structures by heating above the glass transition temperature of the organic film. This patterning process by self-organization is caused by the interplay of dispersion interactions and mechanical stress which leads to spinodal deformation. The dynamic evolution of the structures was investigated by time-resolved light diffraction. By prepatterning the substrate, the direction of the waves can be controlled.
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.
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