PRELIMINARY RESULTS OF BTDF CALIBRATION OF TRANSMISSIVE SOLAR DIFFUSERS FOR REMOTE SENSING
Catherine C. Cooksey, Georgi T. Georgiev, Leibo Ding, James J. Butler
Satellite instruments operating in the solar wavelength region require accurate and precise determination of the optical properties of their diffusers used in pre-flight and post-flight calibrations. The majority of recent and current space instruments use reflective diffusers; therefore, there are numerous Bidirectional Reflectance Distribution Function (BRDF) calibration comparisons with National Institute of Standards and Technology (NIST) and other industry and university-based metrology laboratories. However, based on literature searches and communications with NIST and other laboratories, we know of no Bidirectional Transmittance Distribution Function (BTDF) measurement comparisons having taken place between National Measurement Laboratories (NMLs) and/or other metrology laboratories. On the other hand there is a growing interest toward characterization and using, as calibration standards, transmissive diffusers in support of space, air-borne, and ground-based instruments. Some of current space projects employing transmissive diffusers are Ozone Mapping and Profiler Suite instrument (OMPS) Limb diffuser, Geostationary Ocean Color Imager (GOCI), Ozone Monitoring Instrument (OMI), Tropospheric Emissions: Monitoring of Pollution (TEMPO) and Geostationary Environmental Monitoring Spectrometer (GEMS) diffusers. Hence calibration monitoring and cross-calibrations are needed throughout the solar spectrum requiring extension of the BRDF data sets already existing with BTDF data sets.