提高光学系统分辨率的主要方法是增大光学系统的通光口径，而使用子镜拼接得到一块等效大口径主镜是增大通光口径的常用方法。拼接主镜光学系统入轨后子镜进行展开，展开位置与设计位置偏差大小决定光学系统成像质量好坏，因此需要对子镜展开位置的精度进行分析。使用光学软件对拼接主镜光学系统建模，调整子镜6个自由度的位置误差得到其与系统成像质量的关系曲线。结果表明，针对不同位置的子镜，相同位置误差产生的系统波前误差的均方根（RMS）值大小不同，中层子镜对沿着X轴方向的移动敏感，而外层子镜对沿着Y轴方向上的移动敏感。通过对每个子镜单独分配位置误差与每个子镜分配相同的位置误差两种方式对子镜的展开精度进行误差分配，结果表明在产生相同波前误差的情况下，单独对每个子镜位置误差进行定义的精度相对较为宽松。

The main method to improve the resolution of optical system is enlarging the pupil of the optical system, and segmenting sub-mirrors to get an equivalent large diameter primary mirror is a common way to enlarge clear aperture. After the deployment of sub-mirrors for segmented mirrors optical system on orbit, there is deviation between deployment position and the designed position, which is called position error. The error determines the imaging quality of the optical system. So it is necessary to analyze the precision of the position of sub-mirrors. Optical software is used to model the segmented mirror optical system, and the relationship curves between position error and the system′s imaging quality is got by adjusting position error of six degrees of freedom for sub-mirrors. The results show that root mean square (RMS) values generated by the same position error are different when sub-mirrors are at the different positions. The middle mirrors are sensitive to the movement along X axis direction, and the outer ones are sensitive to the movement along the Y axis direction. Two methods are used to distribute the errors into the sub-mirror position error. One is distributing the position error to each sub-mirror alone. Another is distributing the same position error to each sub-mirror. The results show that the former way has a more relax position error when the generated wavefront errors are the same.