大口径主反射镜支撑结构设计

Design of Support for Large Aperture Primary Mirror

大口径空间反射镜支撑技术是空间相机研制中的关键技术之一。从保证反射镜组件刚度、强度和热尺寸稳定性的角度出发,对某型卡塞格林系统Φ980mm口径主反射镜支撑结构进行了设计。提出采用背部六点支撑,三点为主另外三点为辅的支撑方案,通过在支撑结构中设置柔性环节,从而解决了大口径主反射镜在自重作用下面形精度满足要求而在温变载荷作用下面形精度严重超差的问题。利用有限元分析软件进行了主镜组件的静、动态刚度及热尺寸稳定性分析,并在分析的基础上对支撑结构中的柔性环节结构参数进行修正,在保证支撑刚度的同时降低了重力、装配应力和热应力对面形精度的影响。分析和试验结果表明,主镜在重力和4℃均匀温升载荷下面形精度达到PV<λ/10,RMS<λ/50(λ=632.8nm),主镜组件一阶固有频率为116Hz,动力学环境下最大应力65MPa,各项指标完全满足光学系统对主反射镜的设计要求。

Support technology of large aperture space mirror is one of the key points for space camera development. The influences of stiffness, strength and thermal dimensional stability of the mirror component were considered in the process of support structure design. A support for 980 mm primary mirror in Cassegrain space telescope was designed. The support scheme of six points support on back was proposed in which three points were main and the others were assistant. The problem that surface figure accuracy of large aperture primary mirror meets the demand in the gravity load, but out of errors under the load case of uniform temperature change was solved by adding flexible support. By adopting finite element analysis technique, the static and dynamic as well as thermal characters of primary mirror were analyzed. According to the analysis results, structural parameters of the flexible support were adjusted, and then reduce the influences of gravity, assembly stress and thermal stress on the primary mirror. Analysis and test results indicate that surface figure accuracy of the mirror reaches to PV 〈λ/10,RMS 〈λ/50 （ =632.8 nm）, the first natural frequency is 116 Hz, and the maximum stress is 65 MPa in the vibration test, which can meet the requirements for the primary mirror.