大尺寸矩形反射镜结构支撑是离轴三反消像散(TMA)光学遥感器研制过程中的关键技术难点之一。以某临近空间光学遥感器的760 mm×320 mm 三镜为研究对象，系统分析了环境温度对反射镜面型影响的本质原因，得出了温度适应范围与热膨胀系数差(反射镜与支撑结构)、反射镜接口承载能力、柔性支撑刚度之间的关系，形成了一套大口径光学反射镜结构支撑设计思路。提出了一种基于圆切口柔性铰的两轴正交反射镜柔性支撑结构，利用有限元对反射镜组件的光学面型和模态频率进行了仿真分析，通过正弦扫频实验对反射镜组件的结构频率进行了实际验证。在1g重力和10 ℃温度载荷的共同作用下，反射镜光学面型的最大均方根差(RMS)为13.4 nm，满足所提出的λ 45 ( λ = 632 nm)指标要求。反射镜组件最低阶模态频率的分析值和实验值分别为128.67 Hz和124.1 Hz，满足所提出的不低于100 Hz指标要求。

Support system design for large size rectangular mirror is one of the most challenging technical points during development of off-axis three-mirror anastigmatism (TMA) optical imaging sensor. The rectangular third mirror with the size of 760 mm×320 mm is the study object. Key mechanism of the temperature effect on the mirror′ s optical surface deformation is studied thoroughly. The relationships between temperature range and the mirror blank′ s and back support part′ s linear expansion coefficient difference, mirror blank′ s capacity on interface mechanical load, rigidity of the flex structure which connects mirror blank and back support part, are established. During development of the mirror support system, a two-axis flex support structure which is composed of two perpendicular single axis circular flexures is proposed, and finite element analysis (FEA) is also employed to evaluate the mirror′s optical surface error and model frequency of this mirror sub-assembly. In the mean time, sine scan test is used to verify the FEA result of mirror sub-assembly′s model frequency. Under combination of 1g self gravity load and 10 ℃ temperature variation, the maximum FEA value of the mirror optical surface root-meansquare(RMS) error is 13.4 nm, and it meets the proposed requirement λ 45 ( λ = 632 nm ). FEA result and test value of the lowest model frequency of the mirror sub-assembly are 128.67 Hz and 124.1 Hz, respectively, it is higher than the proposed requirement of 100 Hz and meets design objective.