Each mirror produced by this NASA developed process is a monolithic structure from a single crystal of silicon. Due to single crystal silicon's extraordinary homogeneity and lack of internal stress, we light weight after optical polishing. Mirrors produced by our original process were about 1/4th the mass of an equivalent quartz mirror and were typically 1/50th wave or better. We have recently revised our process, replacing the isogrid structures with ones optimized to minimize distortion due to mounting errors. We have also switched from ultrasonic machining to CNC grinding to enable the production of larger mirrors. We report results to date for mirrors produced by the revised process and cryogenic test results for an ultrasonically light weighted mirror.
In support of Goddard Space Flight Center's (GSFC) Constellation-X mandrel manufacturing effort, a series of fabrication experiments are being performed to determine a best approach, and to supply the project with precision mandrels. Currently, polishing immediately after diamond turning produces a RMS surface roughness of 0.3 nm, on an electroless nickel-plated aluminum mandrel. Studies currently under way will incorporate an abrasive-figuring step to be followed by this polishing operation. The current diamond turning, figuring and polishing procedures will be described and the results presented.
This paper will present measured reflectance, transmittance, surface figure and roughness data for KBr and ZnSe beamsplitters and compensators that were made for use on spaceflight Michelson-type Fourier transform spectrometers. Measured data for visible and infrared wavelengths, at room temperature and cryogenic temperatures, will be shown. Calculated performance data for KCl substrates will be included for comparison.
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