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Stray light test methods for space optical components

The straylight behavior of optical components for space instruments is in practice estimated by the valuation of their surface finish (the RMS roughness Rq) and their contamination. Other artifacts like scratches and bulk scatter can contribute too and cause an increase of the straylight level. This paper discussed several test methods to separate these artifacts from roughness scatter, to identify these artifacts and to process them with the optical code ASAP. These tests methods make use of the fact that roughness scatter shows (a) a fractal behavior, (b) must be a superficies radiator and (c) transfers the polarization components s and p independently from each other. The last condition is used to suppress scatter due to roughness. To emphasize the practical importance of these artifacts no specially prepared samples have been used for this paper. All shown measurements have been selected out of regular test series for several space projects. The tests have been carried out with a ZEISS SLG 110 scatterometer, which is described in paper number 2210-51 of this conference13, at the optical clean room laboratory of ESTEC.