Radiometric calibration of the SwRI ultraviolet reflectance chamber (SwURC) far-ultraviolet reflectometer

The Southwest Research Institute Ultraviolet Reflectance Chamber (SwURC) is a highly capable UV reflectometer chamber and data acquisition system designed to provide bidirectional scattering data of various surfaces and materials. The chamber provides laboratory-based UV reflectance measurements of water frost/ice, lunar soils, simulants, and analogs to support interpretation of UV reflectance data from the Lyman Alpha Mapping Project (LAMP) Lunar Reconnaissance Orbiter (LRO). A deuterium lamp illuminates a monochromator with a nominal wavelength range of 115 nm to 210 nm. The detector scans emission angles -85° to +85°in the principal plane. Liquid nitrogen passed through the sample mount enables constant refrigeration of tray temperatures down to 78 K to form water ice and other volatile samples. The SwURC can be configured to examine a wide range of samples and materials through the use of custom removable sample trays, connectors, and holders. Calibration reference standard measurements reported here include Al/MgF2 coated mirrors for specular reflection and Fluorilon for diffuse reflectances. This calibration work is a precursor to reports of experiments measuring the far-UV reflectance of water frost, lunar simulants, and Apollo soil sample 10084 in support of LRO-LAMP.