Spectral features : How to reduce them

Spectral features are introduced by the diffuser that is used during on-board sun calibration. New findings are presented on how to reduce the size of these spectral features. Reduction can be obtained via optical design of the calibration unit, but also in creating a better diffuser. A novel diffuser design will be presented and its performance will be compared to standard diffusers like an Aluminum diffuser, a Spectralon diffuser, and the QVD (Quasi Volume Diffuser). For the in-house spectral features testing setup an improvement of about a factor of eight was obtained for the new diffuser type when compared to QVD. QVD in its turn is already better than an Aluminum diffuser by a factor of ten. Spectralon and QVD are found to be about equally good when measured in terms of spectral features reduction. The novel diffuser is referred to as SanDiff since it is a sandwich of QVD and PTFE material. For the SanDiff also the BSDF was measured and will be presented here. © 2009 SPIE.