极大望远镜终端仪器结构变形的实时主动补偿方法研究

In order to satisfy the extremely demanding requirements for astronomical observation, designers of these terminal instruments, which mounted at Cassegrain or Nasmyth foci of large telescope, must make efforts to concern the stringent design requirements. As a telescope tracks, the instrument is subject to a varying gravity vector, so instrument structure and components within it must suffer from gravitationally induced flexure to some degree. The issue is becoming more critical as the instrument size tends to scale with the telescope diameter. To solve this problem, an optimized structure design is primarily consideration but not enough. Further improvements in performance can be achieved if the instruments have active compensation for any residual flexure. This project aim to research on the Wide Field Optical Spectrograph (WFOS) of Thirty Meter Telescope (TMT) and developed an active compensation system capable of compensating the instrument flexure using an active real-time correction method. The optical-mechanical modeling of WFOS is used to do the simulation and analysis. With the help of optical sensitivity analysis, choosing the suitable optical element as the active compensation component. Finally, we examine the Active Flexure Compensation (AFC) predicted mechanical performance, in terms of accuracy of flexure compensation. Image motion in large instruments is a long-standing problem which has become acute at the scale of 4-m telescope, this project will solve this problem and demonstrate how open-loop active compensation can be successfully applied to the larger telescope. This project will develop related technology to the construction of large instruments for extremely large telescope in China and promote the fully participation in the TMT to constructing one or two scientific instrument.

配置在极大望远镜上的科学仪器随着天文观测需求的不断提高，对仪器设计提出了更加苛刻的要求。终端仪器由于望远镜运动或自身消旋运动受到不同重力向量的作用产生一定的结构变形，而且随着望远镜和终端仪器自身线性尺寸的变大影响更为剧烈。为了消除结构变形的影响，除了需要进行光机结构的优化设计，还需要进行主动的补偿矫正。本项目主要以三十米望远镜（TMT）宽视场光学光谱仪（WFOS）为背景进行基于实时主动补偿方法实现极大望远镜终端仪器结构变形的主动补偿系统研究。通过WFOS光机模型的建立，仿真分析光谱仪各器件的补偿灵敏度，利用实时主动补偿算法控制主动补偿系统实现结构变形的矫正并给出补偿精度。本项目的研究将解决4米级以上望远镜终端仪器由于结构变形引起的仪器稳定性下降的问题，通过该项研究推动中国全面参与或主导一两个TMT 科学仪器的研制打下基础，也为我国自主发展中国的天文大望远镜和科学仪器增强配套能力。

极大望远镜配备的天文仪器由于重力或温度变化引起的结构变形使得系统最终的成像或光谱信息发生漂移而性能下降，而且随着望远镜和仪器体量的不断变大，结构变形的影响将更为剧烈，除了需要进行光机系统的被动优化设计，还必须考虑主动的补偿来减小影响。本项目以三十米望远镜（TMT）的首光仪器宽视场多目标光谱仪（WFOS）为研究对象，开展了极大望远镜终端仪器结构变形的主动补偿方法研究。通过WFOS主动补偿分析模型的建立，即可获得光谱仪各器件的灵敏度为光学和结构系统的设计提供参考，又可为主动补偿策略可行性的评估提供依据，而且该方法同样适用于其它仪器的分析。另外，本项目在实验室搭建简易光谱仪实验平台，以此来测试利用视场外参考数据点作为主动补偿量的控制依据方法的可行性；同时，通过搭建缩尺模型测试平台，对主动补偿控制系统的实现方式和工程应用进行了探讨，积累了一定的经验。