17 August 2016 Analyzing the impact of vibrations on E-ELT primary segmented mirror
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Abstract
The E-ELT primary mirror is 39m in diameter composed of 798 segments. It is exposed to external large but slow amplitude perturbations, mostly gravity, thermal and wind. These perturbations are efficiently rejected by a combination of edge sensor loop and adaptive optics (AO) in order to leave a small residual wavefront error (WFE). Vibrations induced by various equipment in the observatory are typically smaller amplitude but higher frequency perturbations exceeding the rejection capabilities of these control loops. They generate both, low spatial frequency and high spatial frequency WFE. Especially segment phasing errors, i.e. high spatial frequency errors, cannot be compensated by AO. The effect of vibrations is characterized by excitation sources and transmission of the telescope structure and segment support. They all together define the WFE caused by M1 due to vibrations. It is important to build a proper vibration error budget and specification requirements from an early stage of the project. This paper presents the vibration analysis and budgeting approach developed for E-ELT M1 and addresses the impact of vibrations onto WFE.
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B. Sedghi, M. Müller, M. Dimmler, "Analyzing the impact of vibrations on E-ELT primary segmented mirror", Proc. SPIE 9911, Modeling, Systems Engineering, and Project Management for Astronomy VI, 991111 (17 August 2016); doi: 10.1117/12.2232683; https://doi.org/10.1117/12.2232683
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