大型光学天文望远镜风载作用分析

Wind disturbance study on large astronomical telescopes

风载对光学天文望远镜结构和镜面的作用将直接影响望远镜的面形精度和跟踪指向控制,从而降低望远镜的像质。特别是未来大型望远镜越来越多地采用主动光学技术,风载的作用将是影响主动光学子镜的主动控制及望远镜整体性能的重要因素。回顾了大型望远镜风载作用的分析方法和随机风载的性质,详细介绍了采用风速功率谱密度方法进行随机风载分析的过程和采用有限元方法分析建模的方法;建立了一个拼接镜面主动光学望远镜的完整计算模型,研究了子镜及望远镜整体在风载作用下的静态和动态响应,并分析了风载对镜面面形和望远镜的跟踪指向精度的影响。

Wind loading on mirrors and structures of large optical astronomical telescopes is inevitably to degrade figure accuracy of mirrors and to cause trancking and pointing error of the telescope. It is even more problematic for future giant telescopes that are potentially to implement segmented mirror active optics because wind loading will be the critical influencial issue for the control of the segment mirrors and will finally degrade the overall performance of the telescope. First reviewed are the nature of random wind and usually-used analysis methods of wind loading on large astronomical telescopes. Afterwards, dis- cussed in detail is the analysis method based on Power Spectrum Density （PSI）） of wind velocity from the Finite Element Method （FEM） point of view. To demonstrate the discussion, a telescope using segmented active optics is modeled to investi- gate its responses to both static and dynamic wind loading. Wind response of a segmented mirror is calculated before that performed on the overall telescope. The wind induced degradation of mirror figures is estimated, and further, the tracking and pointing accuracy are given.