Characterization Of Optical Baffle Materials

Abstract

Optical baffle materials will play a critical role in meeting specifications for off-axis stray light rejection and contamination control for a number of planned space-based telescopes. Spire has been developing new baffle materials to meet those specifications. The purpose of this paper is to present the results of optical scatter and reflectance measurements for a number of currently available baffle materials and some new baffle materials developed at Spire [1]. Bidirectional reflectance distribution function (BRDF) measurements were performed in a fully automated, in-air scatterometer at two wavelengths, 632.8 nm and 10.6 microns [2]. BRDF data is presented as in-plane and out-of-plane scans over a direction cosine range of + 0.8. Total hemispherical reflectance (THR) measurements were carried out using a semi-automated spectrophotometer with an integrating sphere over a bandwidth of 400 nm to 1000 nm using a Xenon arc lamp as the source and at 3.39 microns and 10.6 microns using laser sources. A discussion of the performance of these optical baffles will be presented based on the BRDF and THR data, and scanning electron microscope (SEM) micrographs of the baffle surfaces.