Research On Space Cryogenic Optical System For SWIR/MWIR Astronomical Observation

As an important way of remote sensing,infrared technology has been applied to many fields such as astronomical observation,national defense,meterorology,resource exploration and environ-mental protection.In the applications of infrared astronomical observation,high-resolution earth observation and faint objects detection,the instruments should have high sensitivity,which can be improved by working in cryogenic temperature to reduce background radiation.The dissertation focuses primarily on research about cryogenic optical system design,alignment and testing technology.Transmission pathway of self-radiation is analyzed according to the basic properties of infrared optical systems,and numerical model for background is established.Difference of background controlling between astronomical observation and earth observation is analyzed.The effect of background on sensitivity decrease of IR instruments is analyzed,and methods of reducing background are listed.Study on design of large aperture cryogenic optical system is developed to meet the requirements of PAH(Polycyclic Aromatic Hydrocarbons)sky survey.Thermalstructural-optical integrated analysis and iterative design methodologies are used in the design.A cryogenic SiC telescope with 300 mm aperture working in 100 K temperature is designed.Supporting structure of the cryogenic telescope is designed.Different materials are used to realize passive optical athermal design.Supporting structure with cross spring flexible hinge is designed to reduce the deformation of mirror due to large changes in temperature.The flexible supporting structure is optimized via response surface methodology(RSM)base on multi-objective genetic algorithm(MOGA).Alignment and testing technologies of cryogenic optical system is studied with the development of the cryogenic SiC telescope.Study on application of domesticallymade SiC mirror in cryogenic temperature is first carried out.Performances of SiC mirror,mirror with supporting structure and telescope are tested respectively.Performances of SiC mirrors with different preparation technologies are tested.Deformation due to thermal control process is tested and the change of surface figure caused by temperature non-uniformity is analyzed as well.Based on the mentioned studies,a 300 mm aperture SiC telescope working in 100-150 K is developed.According to the test result,wavefront error of the telescope is about 133 nm in 130 K,which is diffraction limit at/above 2 micron.It will be a good basis for further research on space telescope.