Optical-Mechanical-Thermal Integrated Analysis On Optical Component Of Mars Medium Resolution Camera

Mars exploration detector in China consists of a Mars orbiter and a landing patrol,it can simultaneously perform on-orbit observations and landing patrols.Mars medium resolution camera can acquire a medium resolution image with a resolution of 65 m in near-Mars orbit,as the optical payload mounted on a Mars orbiter,its main mission is: Drawing global remote sensing image of Mars;Exploring Martian topography and its changes,including imaging of surface,geological structure and topography.As the optical component of medium resolution camera,medium resolution lens is the core component of imaging,the quality of imaging is directly related to whether the mission of Mars exploration can proceed smoothly.The Mars orbiter works on the orbit of Mars,which is hundreds of kilometers away from the surface.Orbiter faces extremely low pressures and a huge temperature difference between day and night,the transient temperature may affect the optical system and the working environment of optical components will be very harsh.Good temperature control measures can make the environment temperature of the medium resolution lens within a controllable range,so that the medium resolution lens can work normally.Since the external thermal environment may affect the optical imaging quality of medium resolution lens,therefore,at the design stage,the imaging quality of optical lens under thermal disturbance needs to be analyzed and evaluated.The optomechanical integrated simulation method of optical components in Mars orbiter includes the following aspects:1)The optical surface data calculating method was researched,the concept of discrete error was introduced,the discrete error of finite element model was evaluated in the actual case,etc.A homogeneous coordinate transformation method was used to separate the rigid body displacement of the optical mirror,and the program was realized to verify the accuracy.Two kinds of displacement correction methods in Zernike polynomial fitting was introduced and the sag deformation calculation program was realized.2)A Mars orbit model was established to simulate the external thermal environment of the Mars.After the orbital motion parameters were determined,the external dynamical thermal flow input of lens was calculated.Based on this orbit model,the thermal load and temperature variation of the surface node under thermal control conditions and transient temperature field distribution at any time during the operating cycle was obtained.3)According to the external mechanical environment that the lens will suffer from,the mechanical characteristics of lens were simulated,including inertial release,modal response,random vibration,shock spectrum response,and sinusoidal vibration,its mechanical properties in a complex mechanical environment was Verified.4)According to the external thermal environment,the lens surface was analyzed and the data was extracted.Based on the theory of optomechanical integrated analysis,an optomechanical data interface program was programmed by MATLAB.Zernike polynomials were used to fit the surface shapes while SigFit was used to calibrate the accuracy,the fitting results were imported into the optical analysis software for image quality evaluation.The results showed that under the dynamic orbital thermal environment,according to the system transfer function and system wavefront before and after,image quality changes within in an acceptable range.