The optimization of segment’s axial support point for large astronomical telescopes

Yongfeng Song; Liangzhou Chen; Chang Song; Xiaojun Liu

doi:10.1117/12.2511841

7 March 2019 The optimization of segment’s axial support point for large astronomical telescopes

Yongfeng Song, Liangzhou Chen, Chang Song, Xiaojun Liu

Proceedings Volume 11053, Tenth International Symposium on Precision Engineering Measurements and Instrumentation; 110530L (2019) https://doi.org/10.1117/12.2511841
Event: 10th International Symposium on Precision Engineering Measurements and Instrumentation (ISPEMI 2018), 2018, Kunming, China

Abstract

Existing axial support for segments mostly adopts the Whiffletree support mode. The location of the support point will have a great influence on the surface precision of the primary mirror, and then influence the final imaging quality of the telescope. At present, there is no special support technology for traditional and thin mirror.In this paper, the research is based on LOT’s hexagonal segment (the surface is hyperboloid, diagonal line is 1.2m, thickness is 45mm, material is Zerodur), which is designed by Huazhong university of science and technology. The optimization of the Whiffletree axial support point of the segment is carried out. Efficient optimization algorithm is used in the research. After building parameterized model of segment support point location, FEM is used to obtain segment surface deformation. Taking the minimum RMS of deformation on segment surface under gravity as the goal, optimized software ISIGHT is applied to find the best support point location. Zernike orthonormal polynomials for hexagonal pupils is used to remove rigid-body motion. Finally, the best support point location point is obtained, the RMS of the segment surface deformation is 11.56nm and the PV is 63.98nm. The result can meets the requirement of LOT design well.

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Yongfeng Song, Liangzhou Chen, Chang Song, and Xiaojun Liu "The optimization of segment’s axial support point for large astronomical telescopes", Proc. SPIE 11053, Tenth International Symposium on Precision Engineering Measurements and Instrumentation, 110530L (7 March 2019); https://doi.org/10.1117/12.2511841

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KEYWORDS

Zernike polynomials

Optimization (mathematics)

Image segmentation

Mirrors

Astronomical telescopes

Finite element methods

Telescopes

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