22 July 2016 ULE design considerations for a 3m class light weighted mirror blank for E-ELT M5
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It is expected that the next generation of large ground based astronomical telescopes will need large fast-steering/tip-tilt mirrors made of ultra-lightweight construction. These fast-steering mirrors are used to continuously correct for atmospheric disturbances and telescope vibrations. An example of this is the European Extremely Large Telescope (E-ELT) M5 lightweight mirror, which is part of the Tip-Tilt/Field-Stabilization Unit. The baseline design for the E-ELT M5 mirror, as presented in the E-ELT Construction Proposal, is a closed-back ULE mirror with a lightweight core using square core cells. Corning Incorporated (Corning) has a long history of manufacturing lightweight mirror blanks using ULE in a closed-back construction, going back to the 1960’s, and includes the Hubble Space Telescope primary mirror, Subaru Telescope secondary and tertiary mirrors, the Magellan I and II tertiary mirrors, and Kepler Space Telescope primary mirror, among many others. A parametric study of 1-meter class lightweight mirror designs showed that Corning’s capability to seal a continuous back sheet to a light-weighted core structure provides superior mirror rigidity, in a near-zero thermal expansion material, relative to other existing technologies in this design space. Corning has investigated the parametric performance of several design characteristics for a 3-meter class lightweight mirror blank for the E-ELT M5. Finite Element Analysis was performed on several design scenarios to obtain weight, areal density, and first Eigen frequency. This paper presents an overview of Corning ULE and lightweight mirror manufacturing capabilities, the parametric performance of design characteristics for 1-meter class and 3-meter class lightweight mirrors, as well as the manufacturing advantages and disadvantages of those characteristics.
© (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Andrew Fox, Andrew Fox, Tom Hobbs, Tom Hobbs, Mary Edwards, Mary Edwards, Matthew Arnold, Matthew Arnold, Kent Sawyer, Kent Sawyer, } "ULE design considerations for a 3m class light weighted mirror blank for E-ELT M5", Proc. SPIE 9912, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II, 99123F (22 July 2016); doi: 10.1117/12.2235354; https://doi.org/10.1117/12.2235354


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