Research On Micro-vibration Analysis Of Space Optical Telescope Based On Opto-mechanical Integration

Space optical remote sensing technology is widely used in the fields of topographic mapping,resource census and military reconnaissance.In order to obtain clear and intuitive high-quality remote sensing images,higher resolution are required for space telescopes.Increasing the focal length and aperture of the space optical telescope is a direct means to achieve high spatial resolution.However,for the large aperture,long focal length and reflective optical system,its structure has the characteristics of high specific stiffness and low absolute stiffness.In the space microgravity environment,it is vulnerable to the micro vibration generated by various disturbance sources on satellite(solar panel rotating mechanisms,attitude control reaction wheels,etc.).The attitude control reaction wheel is the main disturbance source.During on orbit operation,the internal rotor of the reaction wheel will continue to rotate at high speed and produce disturbing force and disturbing torque with complex frequency components,causing jitter,reducing the on orbit dynamic transfer function of the optical system,resulting in image quality degradation and even inability to image.Therefore,it is urgent to analyze and study the effect of micro-vibration on the imaging quality of the optical telescope at the satellite level,and to evaluate the imaging quality of the optical system in the design stage,the results can be used to guide the structure layout and the design of vibration isolation system.1.The line-of-sight(LOS)error of optical telescope under reaction wheel disturbance is analyzed based on satellite hierarchy.The basic principle of reaction wheel disturbance is studied.Based on the assumption of elasticity,thin plate bending theory and structural dynamics theory,the structural dynamics model of a highresolution satellite is established.The disturbance data of the flywheel is used as the input excitation of the Satellite Structure Dynamics model,and the LOS error of the object/image space of the optical telescope under the disturbance of the flywheel is analyzed by the integrated analysis method.The results show that the primary mirror has the greatest influence on the high resolution optical telescope,and the 8th order mode of the whole satellite has the greatest contribution to the los error,the contribution percentage is 53.737%.2.The dynamics of the primary mirror assembly is analyzed based on linear state space representation.Based on the Modal Analysis Theory and state space theory,the state space model of mirror assembly is established.The Direct Current(DC)gain method is used to reduce the mode to simplify the state space model,and the frequency response characteristics of the mirror assembly are analyzed,which greatly improves the calculation efficiency.The influence of the variation of the surface precision of the Primary Mirror on the modulation transfer function(MTF)of the optical system under the action of gravity load or temperature load is analyzed,nyquist frequency MTF has deteriorated from 0.301060 to 0.056873.3.The influence of reaction wheel disturbance on the imaging quality of optical system is analyzed by using the analysis method of optical mechanical integration.The influence of mirror rigid body motion on image plane image motion and the influence of different forms of transverse vibration on the MTF of optical system are studied.The transient response of the optical satellite is analyzed,and the obtained rigid body displacement and mirror deformation result files of the mirror are imported into ZEMAX to obtain the image quality evaluation results of the optical imaging system such as MTF and point column diagram under the disturbance of the reaction wheel.4.Carry out optical detection test,dynamic vibration test and LOS Error Measurement of space optical telescope.The change of surface accuracy of mirror with high surface accuracy under the action of radial gravity is detected by optical test.The first order natural frequency of the Primary Mirror Assembly is verified by the dynamic test,which reflects the accuracy of the dynamic analysis of the Primary Mirror Assembly.Compared with the experimental results,the relative error of the response displacement obtained by the state space method is 6%.Compared with the experimental results,the relative error of the 8th Order Modal Object Space Angular displacement is 9.34%,which is calculated by simulation.The above research shows that the opto-mechanical integration analysis method is an effective means to analyze the micro vibration of space optical telescope,which can realize the comprehensive evaluation of the imaging quality of the optical system under the micro vibration action of the reaction wheel,and the analysis results can also guide the structural layout and the design of vibration isolation system on the satellite.