22 December 2003 Techniques and uncertainty analysis for interferometric surface figure error measurement of spherical mirrors at 20K
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Abstract
This report describes the facility and experimental methods at the Goddard Space Flight Center Optics Branch for the measurement of the surface figure of cryogenically-cooled spherical mirrors using standard phase-shifting interferometry, with an uncertainty goal of 6 nm rms. The mirrors to be tested will be spheres with radius of curvature of 600 mm, and clear apertures of 120 - 150 mm. The optic surface will first be measured at room temperature using standard "absolute" techniques with an uncertainty of 2.6 nm rms; and then the change in surface figure error between room temperature and 20 K will be measured with an uncertainty goal of 5.4 nm rms. The mirror will be cooled within a cryostat, and its surface figure error measured through a fused-silica window. The facility and techniques are being developed to measure the cryogenic surface figure error of prototype lightweight mirrors being developed by the European Space Agency (ESA) and by US companies in SBIR's for NASA. This paper will present the measurement facility, methods and uncertainty analysis.
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Peter N. Blake, Peter N. Blake, Ronald G. Mink, Ronald G. Mink, David Content, David Content, Pamela Davila, Pamela Davila, Frederick David Robinson, Frederick David Robinson, Scott R. Antonille, Scott R. Antonille, "Techniques and uncertainty analysis for interferometric surface figure error measurement of spherical mirrors at 20K", Proc. SPIE 5180, Optical Manufacturing and Testing V, (22 December 2003); doi: 10.1117/12.508300; https://doi.org/10.1117/12.508300
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