1 April 1981 Alignment And Evaluation Of The Cryogenic Corrected Infrared Astronomical Satellite (IRAS) Telescope
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Optical Engineering, 20(2), 202195 (1981). doi:10.1117/12.7972690
Room temperature alignment and evaluation techniques for the Infrared Astronomical Satellite (IRAS) telescope which has a primary mirror figured to correct for surface distortions at the 2 K operating temperature will be discussed. Interferometric cryogenic testing of the 0.6 meter, f/1 .5 light-weighted beryllium primary mirror at its intended operating temperature revealed surface distortions that could be modeled with Zernike polynomials. With this model, it was possible to derive the -inverse- of the cryo wavefront error (ideal cryo mirror) and figure the cryo correction into the primary mirror using Perkin-Elmer's Computer Controlled Polisher. It was recognized that during room temperature assembly of the system, misalignment of the secondary mirror could introduce additional unwanted aberrations that would cancel or distort the wavefront errors purposely intro-duced by the cryo figuring. To avoid this possible degradation and to ensure optimum telescope performance, the system Zernike polynomial coefficients and wavefront maps generated from the in-process alignment interferograms were monitored and compared to Zernike coefficients and wavefront maps for the cryo corrected primary mirror. Using Zernike polynomials to monitor the optical quality of the telescope enabled figure and alignment errrors to be monitored, and demonstrated that the alignment tolerance was achieved.
Noreen Harned, Robert Harped, Ramsey Melugin, "Alignment And Evaluation Of The Cryogenic Corrected Infrared Astronomical Satellite (IRAS) Telescope," Optical Engineering 20(2), 202195 (1 April 1981). https://doi.org/10.1117/12.7972690

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