Optimization Of The Indicators Of The Space-based Visible Light Detection System

With the coming of the information age,a country’s ability to obtain information is an important embodiment of the country’s modernization level and comprehensive national strength.Spatial information plays an important role in the exploration and use of spatial resources and spatial control.In order to obtain more space information,human’s exploration of space is deepening step by step,and more and more spacecraft are launched into space.Space debris is generated by the launch,loss of control and disintegration of spacecraft,which will pose a threat to the safety of spacecraft in orbit.Space debris and spacecraft are referred to as space objects.The proliferation of space targets has created a crowded space environment.In order to determine the degree of collision threat to the spacecraft in orbit,it is necessary to detect the space target.Space detection system is a ‘sense organ’ for human to obtain space information,and can sense space situation.Space detection system mainly includes ground-based detection system and space-based detection system.Although the ground-based detection system is susceptible to atmospheric interference,it is easy to realize large aperture and highresolution detection.The space-based detection system is free from atmospheric interference and can achieve all-weather detection,but is limited by size and weight.With the increase of human demand for space exploration,space-based detection system has become the focus of the development of various countries,and its main development trend is miniaturization and lightweight.The aperture and field of view(FOV)of space-based detection system determine the size envelope and overall weight of the system.Therefore,on the basis of meeting the detection requirements,it is of great significance to study and select a reasonable threshold aperture and FOV method for the design,efficiency evaluation and application of space-based detection system.This dissertation is devoted to the optimization of the indicators of the space-based visible light detection system,aiming to determine the indicators that can not only meet the requirements of the system detection but also ensure the size and weight limits of the system through a reasonable index determination scheme.On the one hand,the aperture size of the space-based visible light detection system directly determines the radiation energy received by the system.The larger the aperture of the detection system,the higher the detection sensitivity.But as the aperture increases,so does the aberration of the system.Therefore,it is necessary to determine a reasonable aperture of the system.On the other hand,the FOV of space-based visible light detection system determines its detection range,thus affecting the system’s coverage ability and revisit period of space targets.The larger the FOV,the stronger the coverage ability of the target,the shorter the revisit cycle of the system.But the distortion of the system increases with the increase of the FOV.So it is very important to determine a reasonable FOV of the system.Finally,the imaging response uniformity of the system determines the imaging quality.In order to improve the image quality,the imaging response non-uniformity correction of the space-based visible detection system is studied.In order to improve the detection performance of space-based visible light detection system,this dissertation studies the aperture,FOV and relative radiation calibration.The main research contents are as follows:Study on threshold aperture of space-based visible light detection system.By constructing a radiation transfer model based on the effective reflection area model of space targets,the aperture size of the system is limited to meet the detection requirements of the system.A determination scheme of threshold aperture for spacebased visible light detection system is proposed.Firstly,the main radiation sources of space targets in the visible range are determined.Then,taking conical space target as the research object,a three-dimensional radiation transmission model is constructed,and the variation of radiation intensity of the space target received by the detector is analyzed by case.Finally,the threshold aperture of the system is determined based on the requirements of detection probability,false alarm rate,signal-to-noise ratio,ultimate detection magnitude and ultimate detection distance.Research on the threshold FOV of the space-based visible light detection system.With the aim of observing geosynchronous orbit(GEO)objects,and on the basis of improving the observation mode of the space-based visible light detection camera,combined with the theory of orbital design,the threshold cross-orbit field of view(COFOV)and along-orbit field of view(AOFOV)of square field camera is determined separately.A method for determining the threshold FOV of the space-based visible light detection system is proposed.Firstly,by analyzing the evolution of GEO objects,the distribution of their trajectory is obtained.In order to ensure the system coverage while ensuring the system’s miniaturization and lightweight,the small FOV is chosen as far as possible.By improving the natural rendezvous mode,the satellite observation method was determined.Finally,the threshold values of COFOV and AOFOV were determined according to the coverage and revisiting period of the system,and the orbital altitude and orbital inclination of the loaded satellite were determined.Study on response non-uniformity correction for space-based visible light detection system.The relative radiation calibration of a typical space-based visible detection system,a concentric optical camera based on optical fiber relay imaging,was carried out in the laboratory environment to realize the non-uniformity correction of the imaging response of the system.Firstly,in the detection of defect bad point pixels,the inherent defects of image sensor and the inherent defects of optical fiber panel are respectively detected,and a defect detection method of manually binarization segmentation of saturated frames is proposed.Secondly,when correcting the imaging response heterogeneity,the relative response coefficients between the pixels of the flatfield images with different levels of radiation brightness are marked,and the correction coefficients of the imaging response heterogeneity among the pixels are obtained through the experimental data.Finally,the heterogeneity between the pixels before and after correction is analyzed.The results show that the heterogeneity of the pixel response decreases from 10.01% to 0.78% after correction.