Research On Technologies Of Thermal Control For Space Telescope Based On Structural-Thermal-Optical Integrated Analysis

With the increasing demand of space observation,the large aperture of space telescope has become the main development direction.The application of large aperture space telescope has greatly improved the spatial resolution of remote sensing observation and is of great significance to human exploration and cognition of the universe.However,while space telescopes bring many conveniences,they also face the challenge of harsh space environment.For a typical space telescope,it is affected by complex external heat flow and internal heat source during orbit operation,resulting in large temperature fluctuations and temperature uneven distribution of the telescope.Temperature fluctuations and temperature uneven distribution of the optical system can cause thermal deformation of the support structure and optical elements,resulting in translation,tilt and surface distortion of the optical elements,thus reducing the imaging quality.In addition,the temperature of the electronic components also has an important effect on the observation performance of the space telescope.Therefore,an effective thermal control design for a space telescope is the key to ensure that its reasonable temperature level and uniform temperature distribution,so as to obtain good imaging quality.Focusing on the development of the space telescope thermal control system,this paper has carried out research on related technologies such as structural-thermaloptical integrated simulation analysis,thermal design parameter sensitivity analysis,and multi-objective optimization of thermal design parameters.Firstly,the space environment of the orbit where the space telescope is located is analyzed.By calculating the external heat flow received by each surface of the space optical load system under different flight attitudes and Beta angle conditions,the opening position of the heat dissipation surface of the space telescope and the external heat flow conditions of extreme thermal analysis conditions are determined.By analyzing the structural characteristics and mission requirements of the space telescope,the difficulties of its thermal design are found out,and the temperature influencing factors of each key component are analyzed.Based on this,the detailed design of the thermal control system of the space telescope is completed.Secondly,according to the designed thermal control scheme,combined with the basic theory of structural-thermal-optical integrated analysis,the structural-thermaloptical integrated analysis model of the space telescope is established,and the structural-thermal-optical integrated analysis of high temperature condition and low temperature condition is completed.The analysis results show that the modulation transfer function(MTF)of different fields of view of the space telescope at Nyquist frequency is greater than 0.3 in the two extreme thermal environments,but there is still a great decrease compared to the theoretical design value.Therefore,in order to further improve the optical performance of the space telescope and reduce the loss of its imaging quality in the thermal control design stage,it is necessary to optimize the thermal control system.Then,the selected thermal design parameters of the optical system are sampled in their variable space,and the optical performance corresponding to each group of parameters is obtained through the structural-thermal-optical integrated analysis of the space telescope,and on this basis,a surrogate model that can reflect the relationship between the thermal design parameters and the optical performance of the system is established.On the basis of the established structural-thermal-optical integrated surrogate model,combined with the sensitivity analysis theory,the local sensitivity analysis and global sensitivity analysis of the thermal design parameters are carried out respectively with the optical performance as the objective.The qualitative and quantitative analysis results of the sensitivity of the thermal design parameters are obtained,and the thermal design parameters that have significant influence on the optical performance of the system are found out.It provides guidance for the optimization of thermal control system.Finally,the design variables to be optimized are determined according to the results of sensitivity analysis,and the mean and variance of MTF at Nyquist frequency for the 12 fields of view of the space telescope are taken as the optimization objectives.Based on the structural-thermal-optical integrated analysis surrogate model,the multiobjective optimization of the thermal control system is completed by combining three multi-objective optimization algorithms,and the TOPSIS decision method with weights is used to select the compromise solution and the optimal design scheme is determined by comparative analysis.The scheme is substituted into the structural-thermal-optical integrated analysis of the space telescope,and the differences in the temperature and optical performance of the telescope before and after the optimization of the thermal control system are compared.The results show that after the optimization of the thermal control system,the temperature of the main optical elements of the space telescope is closer to the reference temperature of 20℃ under high and low temperature conditions.In addition,the mean values of MTF of the telescope in different fields of view under high and low temperature conditions are increased by 32.1% and 25.6%,respectively,and the variances of MTF are decreased by 43.6% and 46.7%,respectively,which further improves the optical performance of the space telescope and reduces its image quality loss in the thermal control design stage.