Structure Optimization Design And Mechanical Properties Research Of A Space Ultraviolet Large Field Scanning Imager

The wide-angle aurora imager is the first space-based aurora detection ultraviolet imager in China.It is mounted on D-star of FY-3 satellite.It imaged LBH（Lyman Birge Hopfield）band（140nm～180nm）of N₂ radiation in far ultraviolet band of Aurora elliptical region,and obtained the relevant information of atmospheric solar spectrum.This paper focuses on the structure dynamic design of the wide-angle aurora imager.Optimizations of structure designs for key components such as the support,the detector and optical filter are accomplished.Dynamic properties of the integrated camera are analyzed as well.The mechanical characteristics of the camera are determined by support and distribution of components.In this paper,the reasonable layout of the camera and the detailed design of the supporting structure including U-shaped frame,base and motor auxiliary support are completed.The fundamental frequency of the combination of U-frame and imaging system is 208.74Hz.The base is a lightweight conical cylinder,and its fundamental frequency is 548.50 Hz.After set the motor auxiliary support,the dynamic response of the cantilever motor is reduced by more than 80%.the maximum acceleration response of sinusoidal load is 11.87g,which is less than the load that the motor can bear 25g.The motor auxiliary support ensures the safety of the motor in the dynamic environment.Finally,the accuracy of transmission shaft system by the influence of supporting structure is analyzed.Under the temperature load and static load,the maximum deformation between the moving parts of the shafting is 1.2μm,the maximum stress is 27.5 MPa,and the material safety margin is 12.71.The simulation results show that the camera support structure ensures not only the high stiffness of the camera,but also the accuracy of the shafting under the force and thermal load.The detector is the core and key component of imaging system of camera.To avoid damage of the wide angle aurora imager’s detector under space dynamic load,a method of setting a vibration isolator between lens tube and lens frame is put forward.Firstly,the passive local vibration isolation scheme is determined,then the characteristics of impact load and vibration isolation principle are analyzed,and then the vibration isolation design is completed from the selection of vibration isolator,stiffness design and installation method.Finally,the mechanical simulation analysis and mechanical test are carried out.The results of tests are in consonance with the analyses.After the installation of the vibration isolator,the maximum acceleration response of sine test is decreased by 23.70%,the maximum acceleration response of random test is decreased by 52.11%and the maximum acceleration response of shock test is decreased by 48%.The vibration isolation effect is remarkable.The scheme of the detector’s vibration isolation design has great reference value to the vibration resistance design of small mass parts of space camera.High temperature barium fluoride（BaF₂）filter is selected for the wide-angle aurora imager wide-angle to cut off the short wave band.In order to solve the problem of large temperature difference of each optical element and ensure the mechanical safety of filter under dynamic load,the design scheme of partial flexibility and overall thermal insulation of filter assembly is proposed,and the detailed design is completed.The filter is“suspended”and the filter supports are designed with multiple lightweight holes to reduce the heat conduction area and extend the heat transfer path.Titanium alloy material with low thermal conductivity and good stiffness is selected for structural parts.Through the thermal test verification,when the high temperature barium fluoride（Ba F₂）filter is within the operating temperature range,the temperature of each mirror and detector is within the required range of operating temperature.The simulation analysis of temperature stability and mechanical properties are put forward.The results show that the RMS values of the mirrors’surfaces are less than one sixth of the wavelength,the maximum deformation is 0.70μm and the maximum stress is 2.5 MPa.The optical stability and mechanical properties of the lens assembly meet the requirements.The mechanical simulation analysis and vibration test of the wide-angle aurora imager are accomplished,and the test results consist with the analysis data.The first natural frequency of the wide-angle aurora imager is higher than 100Hz.The maximum amplification times of acceleration response is 5.06 in sinusoidal vibration test and 4.21 in random vibration test.The wide-angle aurora imager has no abnormality after the sine vibration,random vibration,impact and acceleration tests,.The test results verify the mechanical simulation analysis and indicate that the structure optimization to improve the mechanical properties of the camera is effective.