Overview of key technologies for segmented mirrors of large-aperture optical telescopes
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摘要:
随着天文探测的不断发展,望远镜的口径越来越大,拼接镜面技术为大口径望远镜主镜的设计提供了一种比单镜面形式更简单可行的替代方案,现已成为大口径望远镜主镜设计的重要途径。本文以詹姆斯·韦伯空间望远镜(JWST)和三十米望远镜(TMT)等典型拼接式望远镜的主镜设计为参考,总结了当前拼接镜面技术的发展现状;并阐述了在大规模子镜背景下,不同子镜拼接方案的性能差异,以及镜面支撑技术和共相检测技术的未来发展趋势,希望可以为我国下一代极大口径光学望远镜的自主研制提供参考。
Abstract:With the continuous development of astronomical exploration, the aperture of telescopes is getting larger and larger. Segmented mirror technology offers a viable and much simpler alternative to a large single monolithic primary mirrors, and has become an important way of designing the primary mirror of large-aperture telescopes. This paper summarizes the current development status of various technologies with reference to the primary mirror design of typical segmented telescopes such as the JWST and TMT, and elaborates on the performance differences and mirror supports of different segmented primary mirror schemes under the background of large-scale sub-mirrors. Potential future development trends of this technology and co-phasing detection technology are provided. This research acts as a reference for the independent development of the next generation of very large aperture optical infrared telescopes in China.
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表 1 不同子镜形状差异
Table 1. Comparison of different sub-mirror shapes
子镜形状 拼接间隙 对称性 子镜种类 制造难度 六边形 较小 六重 多 较大 扇形 小 一般 较少 大 圆形 大 好 少 小 表 2 大型拼接镜面望远镜基本参数
Table 2. Basic parameters of large segmented mirror telescopes
时间选址 名称 主镜 拼接子镜 等效口径/m 材料 形状 数量 尺寸/m 1993 American Keck Ⅰ 10 Zerodur Hexagon 36 1.8 1996 American Keck Ⅱ 10 Zerodur Hexagon 36 1.8 1997 American HET 9.2 Zerodur Hexagon 91 1.15 2005 South Africa SALT 9.5 Glass-ceramic Hexagon 91 1.16 2008 Spain GTC 10.4 Glass-ceramic Hexagon 36 1.9 2008 China LAMOST 4 Zerodur Hexagon 61 1.1 2019 Japan Seimei 3.8 Zerodur Petals 18 1.2 2021 American JWST 6.5 Be Hexagon 18 1.5 — American GMT 21 E6 Circular 7 8.4 — American TMT 30 Zerodur Hexagon 492 1.44 — Europe E-ELT 39.3 Zerodur Hexagon 798 1.4 — China LOT 12 Zerodur Hexagon 84 1.44 表 3 大型拼接望远镜支撑结构
Table 3. Large segmented mirror telescope support structures
Keck HET SALT GTC LAMOST TMT E-ELT 支撑点数 36-pt 9-pt 9-pt 36-pt 18-pt 27-pt 27-pt 轴向支撑 Whiffletree Whiffletree Whiffletree Whiffletree Whiffletree Whiffletree Whiffletree 径向支撑 中心膜片 中心膜片 中心膜片 中心膜片 中心膜片 中心膜片 中心膜片 Warping Harness 手动 无 无 自动 无 自动 自动 促动方式 直接促动 直接促动 移动架 直接促动 直接促动 移动架 移动架 表 4 共相检测技术的性能对比
Table 4. Performance comparison of co-phasing detection technologies
技术分类 Piston
检测Tip/Tlit
检测光瞳
对准粗/精
共相2π
模糊量程
(λ)非共光
路误差像平面 PD Y Y N 精 Y ±λ/2 N PR Y Y N 精 Y ±λ/2 N 光瞳面 SHAPS Y Y Y 粗/精 Y ±λ/2 Y PY Y Y Y 精 Y ±λ/4 Y ZELDA Y Y N 粗/精 Y ±λ/2 Y DHS/DFS Y N Y 粗/精 N ±λ/2 Y PISTIL Y Y N 精 Y 3λ Y 中间面 DIPSI Y Y N 粗/精 Y ±λ/2 N CS Y Y N 精 Y ±λ/8 N -
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