Research on high performance support technology of space-based large aperture mirror

Abstract

A three-point back support structure including cone sleeve, flexible structure and adjustable pad is designed for the space-based mirror support to meet the requirements of small surface shape error, high supporting reliability and stability, of which in-depth study on support principle and engineering realization is conducted in this paper. The error sources which influence the surface shape error of the mirror subassembly with three-point back support is summarized. The mechanism of surface shape variation caused by various error sources is studied. The support structure with high stiffness for alleviating the surface shape error caused by various error sources is designed, which can increase the fundamental frequency of mirror subassembly and protect it from yield failure under the condition of dynamic load. Firstly, the static and dynamic simulation of the three-point back support structure model is carried out by means of finite element analysis. Then the dynamic and partial static experiments are performed using aluminum mirror and actual supporting structure. The results show that the surface shape error of mirror with the three-point support structure is superior to λ/80(λ = 632.8 nm), the displacement of mirror is smaller than 0.015 mm, the inclination angle is smaller than 2″, the mass of the mirror subassembly is smaller than 310 kg. The mirror subassembly has a reasonable modal distribution, the fundamental frequency is 128 Hz, which is much higher than the requirement of 120 Hz. The maximum magnification of the mirror assembly excited by the sinusoidal vibration and the random vibration is 2.51and the maximum stress is 286 MPa under the same working condition, which is much lower than the yield limit of the selected material. A kind of segmented metering assembly method is formed and applied to make sure 2 m space-based large-aperture mirror has lower surface shape error according to the theoretical research results in this paper which the surface shape error of the space-based large-aperture mirror supported by three-point on the back which optical axis is in the horizontal direction in test, installation and adjustment is very sensitive to the deviation between rotating shaft of flexible structure and the neutral plane of the mirror in the direction of the optical axis.