Design And Stability Study Of Optical And Mechanical Structure Of Space-borne Lidar With High-repetition Frequency

The aerosol radiative forcing effect mainly influences the balance of the Earth's radiation through two pathways,mamely aerosol-radiation interaction and aerosol-cloud interaction.However,uncertainty in aerosol-cloud interaction is one of the most important uncertainties in the Earth's radiation factor in the IPCC AR5 report.Space-borne lidar for clouds and aerosols are very suitable for the observation of temporal amd spatial distribution of global cloud and aerosol due to its high orbit,high temporal and spatial resolution,and wide detection range.Due to the characterisitics of small-field,low-energy,and single photon detection of space-borne lidar with high-repetition frequency,it has high requirements on the whole opto-mechanical structure and stability.Therefore,it is necessary to carry out the optimal design and stability analysis of opto-mechanical structure of space-borne lidar with high-repetition frequency.Optimal design and stability analysis of the whole opto-mechanical structure are carried out through the integrated analysis method of optical,mechanical,and thermal.First,a set of design schemes for the whole opto-mechanical system is given according to the desigin requirements of space-borne lidar with high-repetition frequency.Zemax software is used to complete the optical design and optimization of beam expander,receiving telescope and F-P etalon,and obtain the structural parameters of optical components.Opto-mechanical structure of the whole system is laid out.Based on the square frame,the modular design method is adopted to install the receiving unit,transmitting unit and subsequent unit in different positions.Secondly,in order to verify the opto-mechanical systems of space-borne lidar with high-repetition frequency.a set of scale-down prototype verification systems is developed.The detailed design of the opto-mechanical system is carried out on the scaled-down prototype,and the wholed structure model is obtained,and the finite element model is established.Integrated structural-thermal-optical technique is proposed to analyze the structural stability of the whole opto-mechanical structural.The optical performance parameters of the system are the research goals,and the structural and thermal loads under different working conditions are taken as the research objects to complete the stability analysis of the whole systems.The scale-down prototype system has completed the installation and adjustment experiment.Compared with simulation calculation,the relative error is within 6%.The gain ratio calibration experiment was carried out on the system,the result was 1.150.The continuous detection experiment was carried out.Its results show that the system can accurately detect the temporal and spatial changes of cloud and aerosol.At night,the aerosol detection range can reach 22km,and the depolarization ratio can reach 10km.The aerosol detection range can reach 10km,and the depolarization ratio can reach 6km in the daytime.Experimental comparison between the inverted optical thickness and the sun photometer shows that the maximum relative error is 14.121%and the minimum is 0.221%,the average detection error is 4.559%.Finally,based on the analysis and verification results of the scaled-down prototype,the optical-mechanical structure of space-borne lidar with high-repetition frequency is designed and optimized.In order to reduce the influence of thermal deformation on the laser pose,a flexible structure is used for three-point support.The optical-mechanical structure of the beam expander is designed.A new flexible structure is designed to fix the large lens of the beam expander,and reduce the influenced of thermal deformation on its surface and pose.Four orthogonal flexible hinges are designed to fix the beam expander,and reduce the influenced of thermal deformation on its pose.A integration method of optical-mechine of combining topology optimization and parameter optimization is proposed,and an ultra-lightweight design is carried out on the ribbed main mirror.Its weight is 4.4kg,which is 80%less than the solid body and 37%less than the initial lightweights structure.In order to reduce the influence of the thermal deformation of the back plate on the primary mirror surface,a new multi-axis composite flexible structure is designed to support the primary mirror.Its surface profile is better than ?/50(?@632.8nm)in the working direction.The supporting structure of the primary and secondary mirrors adopts the form of a central supporting structure.In order to reduce the influence of thermal deformation on the distance between the primary and secondary mirrors,a new type of C/SiC composite material is used.The influence of machining error and compensation method of F-P etalon on is analyzed in detail.Optical-mechanical structure of temperature-adjusted narrowband filter is desigined.The optimized layout of optical-mechanical structure of space-borne lidar with high-repetition frequency will provide a basis for the subsequent further improvement of the overall structure model and simulation.