Study On Effect Of Optical Aberration On Sub-Pixel Centroid Location Accuracy For Star Sensor

Star sensor is a spatial measurement instrument with the highest the three-axis attitude accuracy of spacecraft in the inertia space,and notable characteristics of the new generation of star sensor includes high reliability,well environmental adaptability,miniaturization,less power consumption etc.Achieving higher accurate star sensor is of great significance to enhance the development of country space technology.In the star sensor system with ultra-high precision,sub-pixel centroid positioning technology is generally used to single-star centroid location accuracy to achieve sub-pixel or even higher centroid location accuracy during the star point extraction process.Single-star centroid location accuracy directly affects the success rate of pattern recognition and output attitude-angle accuracy,and determines the star sensor attitude measurement limit accuracy.In research on the sub-pixel centroid location technique,one centroid location error is selection of spot model of star image energy in the subdivision algorithm.The traditional method ignored the influence of optical aberration,and used the Gauss function to describe the distribution of star spot,which has been unable to meet the requirement of realizing the ultra-high precision star sensor.As the primary factor of constraining star sensor performance,optical system has high demands on the detection aperture and field of view,so the objective existence of optical aberration and complex diversity will lead to differences in the star spot distribution,so as to bigger centroid location error.Therefore,in this paper,the theoretical analysis and numerical simulation are combined to exploring the influence of optical aberrations on centroid location error,and the large field of view,athermal,high-precision star sensor optical system is designed.Main studying tasks are as follows:1.Sub-pixel centroid location technology is studied in details,including its working process,partial subdivision algorithm,noise source and so on.According to discussing the influence of sub-pixel centroid location on the detection capability and measurement accuracy of star sensor,this paper proves the irrationality of Gauss function spot mode and concludes that exploring the effects of optical aberration is the inevitable choice to upgrade the centroid location accuracy.2.Based on the Fraunhofer diffraction theory and Zernike aberration polynomial,this paper analyses the spatial distribution characteristics of star spot in aberrated optical system,and supplements the verification with optical software Zemax.3.By means of numerical analysis and programming,this paper reveals effect mechanism of optical aberration on sub-pixel centroid location accuracy,and The analytical expression of location error is calculated combining with the physical process of centroid location.The result will provide a theoretical basis for suppressing or eliminating the centroid location error for aberration;4.This paper integrates different influence of various aberrations,and the analysis of error will help to guide the latter systematic error compensation,and principle of controlling optical aberration will guide the optical system design of star sensor.5.This paper chooses a complex double-Gauss optical system as the basic structure,including eight optical elements,and then optimizes the design based on the use of CODE V optical software until achieving a high precision optical system of star sensor,which meets a view field of 26°,an F-number of 1.5.