EFFECTS OF SPACE-SHUTTLE FLIGHT ON THE REFLECTANCE CHARACTERISTICS OF DIFFUSERS IN THE NEAR-INFRARED, VISIBLE, AND ULTRAVIOLET REGIONS

Many remote sensing instruments employ diffuse targets for calibration. These targets usually consist of diffusers with high Lambertian characteristics illuminated by a calibrated irradiance source. There is increasing interest in conducting in-orbit radiance calibration checks of remote sensing instruments using sunlight reflected off a diffuser. We report on the effects of space flight on the reflectance properties of polytetrafluoroethylene (PTFE) and aluminum diffuser samples flown on three Space Shuttle flights. These experiments showed good stability of both diffuser types in the visible and near infrared but experienced measurable degradation in the ultraviolet. Degradation varied from flight to flight and seemed to be related to different levels of contamination experienced on the three flights.