Design Of The Primary Mirror And Supporting Structure Of Cryogenic Optical System For Infrared Detection

Research on the origin of the universe,observation of planets and stars,and the exploration of extrasolar galaxies are inseparable from the development of infrared astronomical observations.All the aster in the universe will produce infrared radiation.At present,infrared astronomy is one of the most important methods of space observation,and it is also the main application field and development direction cryogenic optics.The cryogenic optical system has the higher requirements for the design of optical system and mechanical structure.On the one hand,each component and mechanical structure needs to sustain the vibration and overweight at the launch stage,and it needs to be as light as possible to reduce the cost.On the other hand,it also needs to deal with the influence of low temperature.Therefore,it's of great significance to study the space cryogenic mirrors.This paper analyzes and designs the primary mirror and its supporting structure for the 1100 mm space telescope,and expends the research on the whole aluminum camera,in which overall structural design of the principled sample machine with a diameter of 300 mm is given.In this paper,all materials of primary mirror and structural parts are aluminum alloy.Aluminum alloy has its unique advantages as the material of mirror blank.Rapid prototyping and low cost are the advantages of aluminum alloy materials,and the unit cost is much lower than other materials,which are also light and can be designed with a variety of high lightweight rates;at the same time,aluminum alloy has excellent thermal conduction characteristic,and the mechanical properties all increase significantly as the temperature decreases.Aluminum alloy is suitable for integrated design,which promote the development of the whole aluminum cameras.At first,according to the design requirements of the primary mirror of the telescope,and on the basis of ensuring the mirror surface shape,the primary mirror is designed to be lightweight.After comparing whit different lightweight methods,a way of better material distribution and lightweight effect is selected.The structure of the nine-point whiffletree support is determined.And in this paper,the design principle and finite element optimization method are combined,which take the deformation of the mirror surface as the objective function to optimize the position and size of the nine points on the back.Then,the design of the nine-point whiffletree support structure is finished.The component of the mirror support structure designed in this paper is mainly composed of flexible supporting,triangle plate and rotation shaft.Through studying related documents about the principle and design method of flexible supporting,and comparing the characteristics of different support methods,we determine the size of the structure by the traditional empirical design method,make the finite element model,and analyze the results.The structural design of the flexible supporting,triangle plate and rotation shaft is completed,in which the rigid body displacement meets the design requirements.After finishing the design of the reflector and its supporting structure components,the designed mirror and its supporting structure components are simulated and analyzed.In the static analysis,the surface shape of the component under the gravity and the change of temperature at low temperature are observed.The results meet what we need.The RMS value is 28.8nm;in the modal analysis,the first-order natural frequency of the structure is 113.52 Hz,which can avoid damage to the structure when being excited during the launch process,and show dynamic performance.The overall design meets the design requirements.Finally,taking the ?300 mirror as the research object,the overall design of the?300 low-temperature infrared all-aluminum camera is carried out,and an overall structural design plan is determined.The surface shape of the mirror and the overall structure are all meet the requirements;the overall modal analysis is performed,which has good performance.The entire structure meets the design requirements,paving the way for the subsequent development of the whole aluminum camera for the IR.