Photometric Data Acquisition And Analysis Of Space Debris

With the rapid development of aerospace science and technology,space launch activities have become increasingly frequent in recent years.The number,total mass and total area of space debris have snowballed,and the space environment has become increasingly deteriorating.Space debris seriously threatens the operational safety of spacecraft in orbit and seriously hinders the sustainable development of space activities.Major space agencies at home and abroad are actively researching space debris.Space debris detection is the primary data source for other research fields on space debris,and it is also an essential basis for space situational awareness and space traffic management.Ground-based optical telescopes have mature technology,low cost and easy maintenance and are essential for detecting space debris in medium and high orbits.The angle and flux of space debris can be obtained with ground-based optical telescopes to conduct photometric observations of space debris.The angle measurement data can be used for the initial orbit determination and orbit correlation of space debris,and the photometric data can be used to invert the characteristics of space debris.The Weihai Observatory of Shandong University is located at the easternmost point of the Shandong Peninsula,equipped with a 100cm aperture and a 60cm aperture optical telescope.The telescope imaging quality is good,and the mechanical performance is excellent.The Weihai Observatory of Shandong University plans to deploy four 15cm aperture optical telescopes in Muztag in 2022.All these provide convenient conditions for us to carry out photometric observation and research of space debris.Based on the existing equipment conditions of the Weihai Observatory of Shandong University,this paper has carried out systematic research on the theory and actual measurement of space debris photometric observation.Multiple research aspects give us unique insights and solutions.Firstly,this paper systematically analyzes the principle of photometric observation of space debris,including the apparent motion of space debris,the light variation mechanism of space debris,and the imaging of space debris at the telescope terminal.The apparent motion of space debris imposes requirements on the telescope’s tracking mechanism and tracking strategy.Also,it determines the imaging of space debris and background stars in the film.The light variation mechanism and photometric model of space debris are not only the theoretical cornerstone of photometric observation of space debris but also an important prerequisite for the inversion of space debris characteristics using photometry.This paper constructs a photon mapping-based space debris photometric image simulation system based on theoretical analysis,which can generate realistic simulated images of specified debris under specified observation conditions(tracking mode,exposure time,orbit,etc.).Image simulation can guide the formulation of observation strategies,explain some particular observation phenomena(such as the distortion of star images),and provide a complete data set for developing photometric image processing systems.Secondly,to meet the operational requirements of the lm telescope at the Weihai Observatory of Shandong University,this paper explores the intelligent strategy of using a single telescope for post-photometric observation of space debris.It proposes the concept of quality factor to measure the observation efficiency of the telescope.A set of space debris observation strategy formulation procedures is constructed based on analyzing the influencing factors of the quality factor.The program can obtain the latest Two Line Element(TLE)from space-track according to the fragment number and perform the orbital calculation.At the same time,the influence of location,moonlight and other factors on the observation quality-quality factor can be considered.Under the premise,different target combinations and time allocation methods are measured to maximize the efficiency of the telescope.Finally,the optimal strategy is presented to the planner visually and is output after manual screening and confirmation for the telescope to execute.Thirdly,this paper introduces the essential requirements and general flow of space debris photometric image processing and focuses on solving the problem of location and flux extraction of faint and distorted star images.The rapid apparent motion of space debris relative to the background stars causes the star image of space debris or background stars to be elongated,the signal-to-noise ratio is reduced,and the contrast is weakened.The extraction of elongated star images has always been the focus and difficulty of space debris photometric image processing.This paper proposes a method for extracting elongated star images based on template matching.The test is carried out on images and measured images,and the results show that,compared with the traditional threshold segmentation method,the extraction method of elongated star image based on template matching has a higher recall rate and smaller error in location and flow extraction.Finally,this paper explores the inversion method of space debris characteristics based on the light curve,analyzes the existing light curve,and obtains relatively reliable characteristic information such as the attitude and stabilization method.In this paper,the relationship between the photoperiod and the edge period of the fragment spin is theoretically analyzed,and the analysis is carried out in combination with the measured light curve of several spin targets.When the specular reflection of space debris is relatively strong,the luminosity will increase sharply at certain observation angles,which is called the flash of space debris.This paper analyzes the cause of the flash,and the location,amplitude,the relationship between width,symmetry,ascending timescale,descending timescale,and fragment properties yield some valuable conclusions.In addition,this paper also uses the method of machine learning to judge the stability of space debris,and the accuracy and recall rate of the judgment is higher than 90%.