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28 July 2008 Extracting the zero-gravity surface figure of a mirror
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Space-based astronomical instruments such as SIM, the Space Interferometry Mission [1, 2] require high-quality mirrors whose zero-gravity surface figure is specified to nanometer accuracy. Testing, however, necessarily proceeds in 1g, normal earth gravity. Extracting the zero-gravity surface has traditionally been done by combining measurements with the mirror in a number of different orientations, so that the effects of gravity cancel. Here we examine some refinements to that technique, showing that for precise results it is necessary that mount forces as well as gravity forces cancel over the different orientations. These ideas are illustrated with lab experience obtained with a 343 mm diameter spherical mirror (PT-M1), which is a prototype SIM compressor mirror.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
E. E. Bloemhof, J. C. Lam, V. A. Feria, and Z. Chang "Extracting the zero-gravity surface figure of a mirror", Proc. SPIE 7013, Optical and Infrared Interferometry, 70133L (28 July 2008);

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