Research On Noise Processing Technology Based On Small Field Star Sensor

Inertial/celestial integrated navigation has become one of the important methods in today's integrated navigation methods because of its high precision,high autonomy and high reliability.Astronomical navigation through the identification of the acquired star map,to further solve the attitude information obtained.Therefore,the accuracy of astronomical navigation,the accuracy of star map recognition algorithm and star sensor star map quality is directly related.Noise is one of the important factors that affect the quality of the accuracy.Therefore it's of great significance and application value to study the method of processing star image noise to improve the accuracy of astronomical navigation.Nowadays,small-satellite technology is developing gradually,meanwhile the size of astronomical star sensor is also required to be reduced.Therefore,small-field star sensor technology has become increasingly important.The mall field of view of the star sensor can capture fewer stars,and the number of stars is usually not enough to recognize,so we need to expand the field of view to obtain enough stars for attitude solution.The expansion of the field of view needs the assistance of gyroscopes and other instruments.In this process,gyroscope noise is introduced,so a corresponding noise processing method is required.This dissertation,based on the research of star sensor,studies the noise processing method based on the National Natural Science Foundation of China(61573113)and Harbin Innovative Talents Research Fund(2014RFXXJ074).First,we analyze the characteristics of noise in the chart.The noise in the star map mainly comes from the design flaw of the star sensor itself,so it is necessary to analyze the noise characteristics of the star sensor.Based on the mathematical model of star sensor noise with CCD as the sensing element,this paper simulates the noisy star image and analyzes the characteristics of the noise in the star image.Secondly,we analyze the noise and processed noisy image.The star image with noise is different from common people,objects and other images.Therefore,it is necessary to analyze the characteristics of noise in the star image and select the corresponding processing method according to the feature.In this paper,by analyzing the types of noise applied to different noise processing methods,we select the methods which are theoretically applicable to the star image.By analyzing the advantages and disadvantages of different noise processing methods in the processing of the star image,we obtain the characteristics of the noise in the star image.Some star sensor mathematical models and parameters,through the simulation obtained star sensor field size and the relationship between the quality of the star map,and further study of the small field star sensor shooting star map noise characteristics.Aiming at the characteristics of noise in star image,a new noise processing method based on the combination of frequency domain filtering and mathematical morphology filtering is proposed.The effectiveness of the proposed method is verified by simulation.Finally,the noise contained in the extended raster algorithm of star map recognition is analyzed and processed.Due to the small field of view of the small field star sensor,the number of stars in the captured image is usually not enough to calculate the attitude of the aircraft.Therefore,the field of view needs to be expanded so as to capture more stars.However,since the expansion of the field of view requires the aid of a gyroscope,the gyroscope noise is introduced during the expansion process,which affects the relative position of the stars in the field of view and further affects the effect of the star Point position solution to calculate the aircraft attitude.Aiming at the above problems,this paper presents a method to remove noise through field-of-view comparison,and its validity is verified by simulation.The simulation results show that the noise processing method proposed in this paper can effectively remove the noise components of the star image shot by the small field star sensor and reduce the error of the attitude resolution of the small field star sensor caused by the noise of the gyroscope.