风载对大口径光电望远镜跟踪误差的影响分析

发布时间：2018-08-26 15:14

【摘要】：望远镜是天文观测中最重要的仪器。随着对空间观测的不断发展，望远镜建造口径越来越大。而为了更好的观测条件，望远镜台址一般选择在高海拔地区。这两方面因素在提高望远镜观测性能的同时，也为望远镜带来了很多跟踪观测误差，其中一个很重要的误差源是施加在望远镜上的环境风载。风载会引起望远镜的振动，造成望远镜观测系统接收到光束波前整体倾斜。本文重点分析风载对大口径光电望远镜跟踪误差的影响。本文首先理论分析了望远镜跟踪误差的两个重要来源：风载和大气湍流扰动。根据工程光学和望远镜装配理论，分析了望远镜主次镜相对位移造成的像差，得出了得出了风载引起的望远镜跟踪误差主要是由于风载引起的次镜偏心和倾斜造成的。并结合振动力学和大气湍流的时空特性分析了动态风载下的次镜振动模型和大气湍流扰动模型。结果表明，风载引起的望远镜跟踪误差和大气湍流扰动引起波前整体倾斜均可以采用2阶AR模型拟合。其次，在现代功率谱估计算法的基础上提出了一种基于2阶AR模型的搜索迭代算法，通过不断搜索迭代，减小湍流功率谱估计误差，，可以有效地将实验数据中风载引起的望远镜跟踪误差功率谱和大气湍流扰动引起波前整体倾斜功率谱分离开，实现风载引起的望远镜跟踪误差的分析。最后在1.8m望远镜平台上，利用风速风向仪实时测量环境风载，采集了三种典型模式下望远镜的跟踪误差。并且应用基于2阶AR模型的搜索迭代算法分析实验数据，得到了风载对望远镜跟踪误差功率谱。验证了望远镜的跟踪误差与风载的风向和风速直接相关，风载对望远镜的作用点是在桁架系统而不是望远镜镜筒。本文的理论分析和实验结果，可以帮助我们更加精确的认识和分析风载对望远镜跟踪误差的影响，为未来望远镜的抗风载结构设计提供参考。
[Abstract]:The telescope is the most important instrument in astronomical observation. With the development of space observation, the construction aperture of the telescope is becoming larger and larger. For better observation conditions, the telescope site is generally chosen in high altitude areas. One of the most important error sources is the ambient wind load applied to the telescope. Wind load will cause the vibration of the telescope and cause the whole tilt of the beam front received by the telescope observation system.
In this paper, two important sources of Telescope Tracking error, wind load and atmospheric turbulence disturbance, are analyzed theoretically. According to the theory of Engineering Optics and telescope assembly, the aberration caused by the relative displacement of the primary and secondary telescope is analyzed. It is concluded that the tracking error of the telescope caused by wind load is mainly due to the offset sum of the secondary mirror caused by wind load. The secondary mirror vibration model and turbulent turbulence model under dynamic wind load are analyzed in combination with vibration mechanics and atmospheric turbulence time-space characteristics. The results show that the tracking error of the telescope caused by wind load and the integral tilt of the wavefront caused by atmospheric turbulence can be fitted by the second-order AR model.
Secondly, on the basis of modern power spectrum estimation algorithm, a search iteration algorithm based on 2nd-order AR model is proposed. Through continuous search iteration, the error of turbulent power spectrum estimation can be reduced. The power spectrum of telescope tracking error caused by wind load and the integral tilted power spectrum caused by atmospheric turbulence can be effectively divided into two parts. The tracking error of the telescope caused by wind load is analyzed.
Finally, on the 1.8m telescope platform, the tracking errors of the telescope under three typical modes are collected by real-time measurement of ambient wind loads with wind speed anemometer, and the tracking error power spectrum of the telescope under wind load is obtained by using the search iteration algorithm based on the second-order AR model. Wind direction is directly related to wind speed, and wind load acts on the telescope in the truss system rather than the telescope tube.
The theoretical analysis and experimental results in this paper can help us to understand and analyze the influence of wind load on the tracking error of telescope more accurately, and provide a reference for the design of wind-resistant structure of future telescope.
【学位授予单位】：中国科学院研究生院（光电技术研究所）
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TH751

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