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. 2023 Jun 8;23(12):5441.
doi: 10.3390/s23125441.

Optimization Design of Large-Aperture Primary Mirror for a Space Remote Camera

Xiaohan Liu  1 , Kaihui Gu  1 , Meixuan Li  1 , Zhifeng Cheng  2
Affiliations

Optimization Design of Large-Aperture Primary Mirror for a Space Remote Camera

Xiaohan Liu et al. Sensors (Basel). .

Abstract

Lightweight, high stability, and high-temperature adaptability are the primary considerations when designing the primary mirror of a micro/nano satellite remote sensing camera. In this paper, the optimized design and experimental verification of the large-aperture primary mirror of the space camera with a diameter of Φ610 mm is carried out. First, the design performance index of the primary mirror was determined according to the coaxial tri-reflective optical imaging system. Then, SiC, with excellent comprehensive performance, was selected as the primary mirror material. The initial structural parameters of the primary mirror were obtained using the traditional empirical design method. Due to the improvement of SiC material casting complex structure reflector technology level, the initial structure of the primary mirror was improved by integrating the flange with the primary mirror body design. The support force acts directly on the flange, changing the transmission path of the traditional back plate support force, and has the advantage that the primary mirror surface shape accuracy can be maintained for a long time when subjected to shock, vibration, and temperature changes. Then, a parametric optimization algorithm based on the mathematical method of compromise programming was used to optimize the design of the initial structural parameters of the improved primary mirror and the flexible hinge, and finite element simulation was conducted on the optimally designed primary mirror assembly. Simulation results show that the root mean square (RMS) surface error is less than λ/50 (λ = 632.8 nm) under gravity, 4 °C temperature rise, and 0.01 mm assembly error. The mass of the primary mirror is 8.66 kg. The maximum displacement of the primary mirror assembly is less than 10 μm, and the maximum inclination angle is less than 5″. The fundamental frequency is 203.74 Hz. Finally, after the primary mirror assembly was precision manufactured and assembled, the surface shape accuracy of the primary mirror was tested by ZYGO interferometer, and the test value was 0.02 λ. The vibration test of the primary mirror assembly was conducted at a fundamental frequency of 208.25 Hz. This simulation and experimental results show that the optimized design of the primary mirror assembly meets the design requirements of the space camera.

Keywords: compromise programming method; finite element simulation (FES); lightweight structure; optimized design; primary mirror.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The coaxial triple reflection optical system layout.
Figure 2
Figure 2
The MTF of the coaxial triple reflection optical system (Nyquist).
Figure 3
Figure 3
The initial structure of the primary mirror.
Figure 4
Figure 4
The initial structure of the primary mirror after a process improvement. (a) stereogram; (b) cutaway view.
Figure 5
Figure 5
The optimization parameters of the primary mirror and the flexible hingle. (a) Primary mirror optimization parameters; (b) The flexure hinge optimization parameters.
Figure 6
Figure 6
The optimized primary mirror assembly and flexible hinge structure. (a) The primary mirror assembly; (b) the flexure hinge.
Figure 7
Figure 7
The finite element mesh model of the primary mirror assembly.
Figure 8
Figure 8
The optimized surface shape error cloud of the primary mirror under the six load cases. (a) X gravity; (b) Y gravity; (c) Z gravity; (d) 4 °C temperature rise; (e) 0.01 mm assembly error in Y; (f) 0.01 mm assembly error in Z.
Figure 8
Figure 8
The optimized surface shape error cloud of the primary mirror under the six load cases. (a) X gravity; (b) Y gravity; (c) Z gravity; (d) 4 °C temperature rise; (e) 0.01 mm assembly error in Y; (f) 0.01 mm assembly error in Z.
Figure 9
Figure 9
The results of the first six natural modes of vibration analysis. (a–f) The first to sixth vibration shape diagram.
Figure 9
Figure 9
The results of the first six natural modes of vibration analysis. (a–f) The first to sixth vibration shape diagram.
Figure 10
Figure 10
The displacement frequency response curves in X directions.
Figure 11
Figure 11
The primary mirror blank. (a) The front; (b) the back being machined.
Figure 12
Figure 12
The surface shape error test of the primary mirror before coating.
Figure 13
Figure 13
The surface shape error test cloud of the primary mirror.
Figure 14
Figure 14
The X-direction vibration results.
See this image and copyright information in PMC

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