Optical-Mechanical Design Of Large Aperture Thermal Insensitive Star Sensor

A star sensor is a kind of sensor which uses starlight for positioning and attitude measurement.It is widely used in the astronomical navigation system.Due to the influence of solar radiation and earth albedo,the operating temperature environment of the star sensor will change to a certain extent.As an important part of the star sensor,the optical system is used to image stars.The imaging quality of the optical system directly affects the detection ability of the star sensor.Usually,the temperature change can affect the imaging quality of the optical system,and a good optical and mechanical design can minimize the influence of temperature on the optical system.Therefore,it is of great significance to research on the optical and mechanical design of the star sensor.In this thesis,the research status of star sensors at home and abroad in recent years is reviewed.Based on the confirmed parameter requirements,the selection and design of a heat-insensitive optical system are carried out.According to the characteristics of the thermal insensitive optical system to carry on the optical mechanical design,through the analysis of the advantages and disadvantages of different structural forms,the design of the appropriate structure,and the mechanical structure collocation can meet the requirements of the thermal insensitive system of materials.To verify the rationality of the design structure,the optical,mechanical and thermal integrated analysis is carried out.The optical,mechanical and thermal integrated analysis can get more accurate simulation results,which is conducive to feedback on the accuracy of the optical and mechanical design,and conducive to the subsequent installation and adjustment experiment of the system.Firstly,MSC.Patran and Nastran software were used for modal analysis to verify the rationality of the structure.Secondly,the rigid body displacement of the node after thermal deformation is calculated by temperature analysis of the structure.Then,the Zernike polynomial coefficients of each deformed lens surface were obtained by Sigfit optical interface software.Finally,the results are imported into Zemax to predict the influence of lens surface shape change and rigid body displacement on the dispersion spot,optical axis stability and other parameters.The energy concentration(within 3×3 pixels)reaches 80 %,the optical axis stability is 0.05 ",the relative distortion is 1.397 %,and the centroid color deviation is less than 5 μm.Finally,the system performance is verified to meet the requirements of the index through the installation test in the temperature range of 20±5 ℃.The total mass of the system is determined to be 9.8 kg,the focal length is 908 mm,the entrance pupil diameter is 200 mm,the energy concentration(within 3×3 pixels)is greater than 80 %,the optical axis stability is higher than 1 ",and the relative distortion is less than3%.The color deviation of the centroid is less than 5 μm,which meets the requirement of the index.Therefore,this paper verifies the accuracy of optical,mechanical and thermal integrated analysis,and provides a set of accurate and fast optical,mechanical and thermal integrated analysis processes for the same type of research.