为了充分分析三十米望远镜(TMT)巨型可控科学反射镜(GSSM)系统平面镜面形精度与跟踪指向精度要求, 需要对其建立完善的系统误差模型。本文采取自上而下的系统误差分配方式, 基于TMT望远镜系统的标准化点源敏感性(PSSn)指标, 利用其良好的合成与分解特性, 对技术指标进行理解与分析, 最终转换为平面镜面形精度与跟踪指向精度要求; 另一方面对影响系统性能的扰动因素进行了分析, 对于静态误差, 利用有限元分析结果, 比较了重力印透与大气扰动对PSSn的影响, 对动态误差而言, 使用系统传递函数进行系统性能评价。最后, 提出了各个关键部件的指标要求, 建立了GSSM的系统误差模型, 结果满足TMT望远镜系统要求, 可作为开展GSSM系统研制的依据。通过分析系统静态误差和动态误差与PSSn的关系发现: 当r0小于0.1 m时, 视宁度对 PSSn 的影响较大; 只有在大气视宁度较好的情况下, 镜面印透才可以发挥作用。随着振动幅度的增加, 系统传递函数退化, 其PSSn会从0.996相应地减少到0.992。通过本文研究可以得出, PSSn作为下一代望远镜性能评价与误差分配指标有着特有的优势, 其独特的合成特性与频域计算方法, 可以对下一代望远镜的建设做出巨大贡献。

To fully analyze precision requirements of surface figure precision and pointing accuracy of plane mirror for the Giant Steerable Scientific Mirror (GSSM) system of this Thirty-Meter Telescope (TMT), system error model of GSSM needed to be established. In this paper, up-to-down distribution mode of system error was adopted. Technological indexes were understood and analyzed and converted to precision requirements of surface figure precision and pointer accuracy of plane mirror, according to standardized Point Source Sensitivity (PSSn) with its good features of synthesis and degradation. On the other hand, disturbance factors affecting system performance were analyzed, and influence of gravity print-through and atmosphere disturbance on PSSn was compared by using analysis result of finite elements for static error. System performance evaluation was conducted with systematic transfer function for dynamic error. Finally, Index requirements of all key components were proposed, and system error model of GSSM was established to satisfy system requirements of TMT as basis for GSSM system development. The experiment results indicate that seeing condition is good (r0<0.1 m), influence of seeing on PSSn was great; mirror print-through could only exert its functions on condition of good atmosphere seeing. With increase of vibration amplitude, system transfer function degenerated, and its PSSn would also reduce correspondingly from 0.996 to 0.992. It can be found that PSSn has special advantages as the next index of performance evaluation and error distribution of telescope, and its unique synthesis features and frequency domain calculation method can contribute greatly for telescope construction of the next generation.