Research On The Pointing Correction Of Telescope Based On Astronomical Orientation Technology

With the continuous development and progress of science and technology,the manufacturing accuracy and detection ability of optical telescopes have been greatly improved,and their applications have also extended to many fields,such as laser communication,space target surveillance,in-orbit target tracking,astronomical observation and so on.Larger aperture mirror can effectively improve telescope angular resolution,limited detectivity and other indicators,while the pointing accuracy of telescope is facing great challenge.The pointing accuracy is affected by many factors in the manufacturing,installation and environment,resulting in the decrease of observation accuracy and efficiency.Therefore,the pointing accuracy is the key index to evaluation the performance of telescope,and the pointing error correction of telescope has become one of the important research fields.The traditional way to improve the pointing accuracy is mainly by improving the stiffness of telescope structure,machining accuracy of mechanical parts,replacing high resolution encoder,etc.However,this way has gradually approached the processing and manufacturing limit of each component,which is difficult to further improve.At the same time,too precise parts also put forward more stringent requirements for processing technology,which is not conducive to the routine maintenance of telescopes,resulting in a surge in manufacturing costs.The celestial bodies on the celestial sphere are widely distributed in the global area,and their position can be accurately calculated,which is an ideal standard source for the correction of telescope pointing error.The astronomical orientation technique estimates the pointing according to the position of the celestial body with higher accuracy,and does not need to establish pointing model of the telescope.Based on astronomical orientation technique,it is possible to correct the telescope in real time with arc seconds or even sub-arc seconds levele.At present,this method is the main way to correct the pointing with high precision,which has high research value and application value.The telescope studied in this dissertation has the characteristics of many dark stars in the image,large field of view,requirement for high accuracy of pointing and fast in running speed.Combined with the specific working environment and requirements of laboratory equipment,some problems in the process of astronomical orientation are discussed.Among them,high robust star identification algorithm,optical system distortion correction and real-time pointing correction are studied.The details are as follows:Firstly,the algorithm of star identification in astronomical orientation is studied.After analyzing the advantages and disadvantages of the traditional star identification algorithm,and combined with the engineering environment and requirements,a high robust star identification algorithm is proposed to solve the problem of accurate identification when some telescope parameters contain errors or even missing.According to the test results,the key indexes of star identification algorithm,such as running speed,detection rate,false alarm rate,missing alarm rate and robustness,are analyzed.Secondly,a new distortion correction method is established based on the formula converted from the horizontal coordinate system to the pixel coordinate system and the correlation between the error sources.This method is based on simulated annealing algorithm,which can estimate the pointing,distortion and multiple telescope parameters at the same time.The algorithm is tested by a real star image,and the running speed,accuracy and stability of the correction results are analyzed.Thirdly,on the basis of the optimal estimation results of the distortion coefficient and related parameters of the telescope,this dissertation proposes a fast pointing correction method.The validity,speed and accuracy of the corresponding correction method are tested by two sets of data,after that the corresponding results are analyzed and discussed.In summary,some key problems in pointing correction of telescope are studied and discussed in this dissertation.At the same time,in view of the similarity of structure and principle,some methods in this dissertation can provide reference-worthy experience for other platforms' photoelectric tracking equipment,such as pointing correction,distortion correction,star identification,etc.