The in-flight radiometric calibration of satellite multispectral sensor for earth and atmospheric observations can be conveniently based on solar diffusers. Theoretically, a knowledge of the spectral bi-directional scatter distribution function (BSDF) of the diffuser panel, and the solar incidence angle is all that is needed to allow the retrieval of the earth albedo in the observed direction. At the request of the ESA, the Centre Spatial de Liege, with the support of Officine Galileo as subcontractor, is currently designing a high-versatility high-accuracy BSDF measurement set-up with application to the calibration of space solar diffusers. This instrument will allow a BSDF measurements uncertainty within 1 percent for any angle in the wavelength range from 200 nm to 2400 nm. Vacuum measurements, polarization analysis capabilities and thermalization of the test sample between 200K and 300K are other unique features of this set-up.
|