Papers by Keyword: Space Telescope

Abstract: In order to design a large aperture primary mirror with the diameter of 1150 mm, the parameters impacting on gravity deformation of the mirror were analyzed and discussed in detail, including material selection, diameter-thickness ratio, the number of the support points, location selection and lightweight structure, etc. A novel space mirror structure system was put forward, and its back was opened and supported by six points on back. The dynamic and static and thermal characteristics were analyzed based on the finite element method. Analysis results showed the surface figure accuracy reached to RMS 14.5nm under the action of gravity load along the optical axis direction and the first-order natural frequency was 214Hz which met to the designed indexes requirements.

Abstract: Structural design of large aperture mirror is one of the key technologies for space telescope development. To meet the requirements of high stiffness, strength and thermal dimensional stability, some factors such as support scheme, materials selection, lightweight design and flexible support design were taken into account. The three supports location of the mirror was determined according to the modal analytical solution. By adjusting the parameters of flexure hinge, influences of gravity, assembly stress and thermal stress on the mirror were reduced obviously. Finite element analysis (FEA) results indicate that the surface accuracy reach to rms10.2nm and 10.8nm under the gravity along optical axis direction and 5°C uniform temperature rise respectively, the fundamental frequency of the mirror component is 268Hz. Dynamics test shows that the first order natural frequency is 256Hz, which shows an error less than 5% compared to FEA results.

Abstract: Lightweight mirrors of SiC (Silicon Carbide) are currently used for numerous space telescopes. The most favorable characteristics of the material are high specific stiffness, high thermal conductivity and low thermal expansion (CTE). For large-scale SiC mirrors, however, the machining cost is very high using traditional polishing process. In this study, a large-scale SiC spherical mirror (φ360mm) was designed as reducing-weight structure with many open-back triangular cells. The ELID mirror grinding technique was conducted to finish the mirror. A unique jig composed of many hydrostatic actuators was developed for reducing the deformation resulted from the grinding force. By using an on-machine measurement system, the form error of the finished surface was measured. The surface roughness of the mirror was also examined with a mobile AFM. As result, a high quality mirror surface, which has form accuracy 0.8µm P-V and roughness of Ra 7.8nm, was achieved. This paper presents the experimental procedure and results.