Research And Realization Of The Key Technology Of Space Debris Laser Ranging

Space debris is the product of human space activities.With the increase of human space activities and the collision and disintegration of space debris,the number of space debris will further increase,and the collision probability between space debris and spacecraft in orbit will continue to increase.In order to ensure the safe operation of manned spacecraft,space station and all kinds of satellites,it is imperative to track and monitor space debris with high precision.As a kind of space technology with the highest precision in space target tracking technology,laser ranging technology has been used in space debris detection all over the world.Its detection principle is basically the same as that of satellite and other cooperative targets,but there are still obvious differences in actual observation.Space debris has the characteristics of poor prediction accuracy,fast speed and short arc time,and the laser ranging system can only detect space debris by receiving diffuse reflection echo,so the effective echo signal is very weak.Therefore,in order to meet the detection requirements of space debris laser ranging system,it is necessary to solve the key problems of laser ranging system in the detection of space debris according to the characteristics of space debris,so as to improve the detection success rate of space debris.In this paper,the structure and detection principle of space debris laser ranging system are systematically studied.On this basis,three key issues are studied,including the pointing correction of space debris laser ranging telescope,real-time identification of weak signal in space debris laser ranging,and effective data extraction of weak signal in space debris laser ranging.Firstly,the BP neural network model optimized by GA and LM algorithm is proposed to correct the pointing error of laser ranging telescope;then,the weak signal of space debris laser ranging is identified in real-time by using the method of primary filtering and linear fitting;after that,the observation data of the weak signal of space debris laser ranging is preprocessed by using random Hough transform model,which realizes the automatic extraction of the effective data of the weak signal;finally,using the Beijing Fangshan laser ranging system as the experimental platform,the test and analysis of the theory and algorithm are carried out through a large number of satellites and space debris observation data to verify the effectiveness of the model.The main achievements of this paper include:1.In the process of using laser ranging technology to detect space debris,the pointing accuracy of the telescope is an important factor affecting the success rate of space debris detection.Aiming at the problem that the current pointing error correction model of laser ranging telescope is difficult to meet the detection requirements of space debris laser ranging system,this paper proposes to use GA and LM algorithm to optimize BP neural network model to correct the telescope pointing error of space debris laser ranging system.The model was modeled by the observation data of stars in the hemispherical area of the station,and the accuracy of the model was verified by the observation data of satellites and space debris.The results show that the accuracy of the BP neural network model optimized by GA and LM algorithm is better than that of the traditional telescope pointing error correction model.At the same time,it overcomes the shortcomings of slow convergence speed and easy to fall into the local optimal solution of the traditional BP neural network model.Compared with the traditional telescope pointing accuracy model,the pointing accuracy of the modified telescope can reach 2.42 "and 1.44" in azimuth and elevation directions,which is improved about 6 times,and it is also of great significance to improve the success rate of space debris detection.2.In order to solve the problem that the signal real-time identification model used in space debris laser ranging system is difficult to meet the detection requirements of this system,this paper proposes to use the combination of primary filtering and linear fitting for real-time identification of weak signals.The model is verified by the observation data of low earth orbit satellite,medium earth orbit satellite,high earth orbit satellite and space debris through Beijing Fangshan laser ranging system.The experimental results show that the real-time identification model of weak signal proposed in this paper can quickly and accurately realize the real-time identification of weak signal,and the identification accuracy is improved qualitatively compared with the current secondary filtering identification algorithm,and the identification error can be controlled within 10%.The identification efficiency of the algorithm is equivalent to that of the secondary filtering algorithm,which provides a strong guarantee for Beijing Fangshan laser ranging system to improve the detection success rate of space obj ects,especially space debris.3.The effective data processing of the echo signal of laser ranging technology is to preprocess the observation data to generate the data format required by the international laser network after obtaining the laser ranging observation data.In the process of data preprocessing,the noise points in the data need to be eliminated,only the effective echo is retained,and then the standard point data is generated by fitting.However,in the process of noise point elimination,most of the laser observation stations still use the method of artificial screen identification,which is too dependent on manual,and can not guarantee the accuracy and quality of the data.Therefore,in this paper,the random Hough transform model is used to automatically extract the effective data from the observation data of laser ranging,and the observation data of Beijing Fangshan laser ranging system is used to verify the extraction effect of the model.The experimental results show that the effective echo data extraction model proposed in this paper can achieve automatic extraction of data,ensuring the stability of data preprocessing accuracy of Beijing Fangshan laser ranging system,and improving the efficiency of data processing,which has important application value to realize automation of laser ranging technology data preprocessing.