Three auto-collimating flats (ACFs) of 1.5 meter clear aperture are being manufactured for use in the JSC Cryo-Optical Metrology test of the James Webb Space Telescope. In-process interferometric testing of the ACFs is used to guide their surface-figure processing. The surface measurement is performed in a vacuum chamber at both room (+20 degrees C) and cryogenic (-240 degrees C) temperatures. With a 12-inch beam diameter FizCam interferometer, sub-aperture measurements are ...
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