Ratioing radiometer, solar diffuser system for in-flight calibration of multispectral satellite sensors

Abstract

One promising way to calibrate a satellite sensor in flight is to place a sun-illuminated white diffuser panel in front of it. However, even if the panel is only deployed for brief periods, it may degrade in the space environment. A ratioing radiometer to monitor the panel changes is described and an error analysis associated with the use of the radiometer is presented. The procedures used to test the optical properties of different candidate panel materials are described. Results of spectral directional-hemispherical reflectance, bidirectional reflectance, polarization and depolarization measurements are presented for nine panel candidate materials before and after exposure to proton and ultraviolet radiation. In this preliminary evaluation it was found that, although polytetrafluoroethylene materials exhibited the most desirable characteristics before proton and UV irradiation, IITRI paint YB-71 withstood proton and UV irradiation the best and is the choice among the nine materials tested.