CGST 主副镜高精度对准方法研究

8m Chinese Giant Solar Telescope(short as CGST)is a plan for the next generation ground-based large solar telescope in China. For realizing the optical quality of diffract-limited imaging and high accuracy of telescope pointing and tracking, the alignment error between primary and secondary mirror should be controlled no more than same of 10 micro-meter. But it is very hard to achieve this requirement only by the active optics with only wave-front sensing. For this result, we plan to attach a laser distance meteorology to the active optics system to realize the alignment error requirement. A important characteristic of this method is high accuracy and control band-pass. So this method can reduce the difficult of telescope structure design in wind buffeting and flexure. The finally benefit is the reducing of total weight of the telescope system. In this proposal, the accuracy, dynamical range and band-pass of this method is researched by the following three aspects: the geometrical characteristic of the laser meteorology, developing of the laser ranging module, and the effect of local seeing condition. The goal of this proposal is to validate this method by theoretical analysis and principle experiment.

8米环形太阳望远镜（简称CGST，Chinese Giant Solar Telescope）是我国下一代地基大口径太阳望远镜建造计划。为了保证光学系统的衍射极限成像质量和望远镜的指向与跟踪精度，CGST主副镜对准精度被要求达到10微米量级。单独依靠基于波前探测的主动光学技术是难以实现该要求的。为此，本项目研究提出通过在主动光学系统中附加激光干涉距离测量手段实现以上精度要求。该方法的特点在于高精度和高控制带宽，一旦成功将极大的降低望远镜结构在抗风振上的设计要求，最终降低望远镜机械结构的总质量。本项目将从激光干涉测量方法的几何特性，激光测量模块的开发，以及局地大气湍流的干扰三个方面研究该方法的测量精度、动态范围和工作频率。本项的研究目标是过理论分析和原理实验证明该方法的有效性。

8米环形太阳望远镜（简称CGST，Chinese Giant Solar Telescope）是我国下一代地基大口径太阳望远镜建造计划。为了保证光学系统的衍射极限成像质量和望远镜的指向与跟踪精度，CGST主副镜对准精度被要求达到10微米量级。单独依靠波前探测的主动光学技术是难以实现该要求的。为此，本项目针对中国巨型太阳望远镜CGST主副镜对准需求，提出了基于激光干涉测距的激光桁架主动对准方法。研究提出通过在主动光学系统中附加激光干涉距离测量手段实现以上精度要求。望远镜运动分析与光学建模表明，在可见光波段，当激光桁架的测距不确定性在5微米以内，环境温度梯度小于0.381K/米时，由对准误差引起的波前RMS好于1/10波长。另外，在Kolmogorov湍流和典型昼间近地面湍流条件下，大气湍流并不会严重降低激光桁架测量的灵敏度。因此，激光桁架测量方法能够满足CGST的副镜主动对准需求。