Star Centroid Estimation and Star Identification of High Accuracy Star Tracker
|School||National University of Defense Science and Technology|
|Keywords||Star sensor Star point positioning Star Pattern Recognition Systematic errors Photon shot noise Photoelectric sampling noise Fourier transform correlation Optical joint transform correlator|
Star sensor attitude measurement devices is a stellar observations provide three-axis attitude information, has the advantage of absolute measurement and high precision, widely used in various types of spacecraft attitude measurement and independent attitude control. With the the observed mapping satellite, deep-space exploration satellite attitude measurement accuracy requirements increase further enhance the star sensor accuracy is one of the important topics facing. This paper combines the high accuracy star sensor actual demand, focus on the star sensor point extraction and star pattern recognition aspects of precision, to explore ways and means of the extract and star charts to identify links to further improve the accuracy of the star sensor in star point . Recognition rate of extraction accuracy star chart paper mainly improve the star sensor point of view, the theoretical analysis and experimental analysis of organic combination of star point to extract error mechanism and high-precision star point extraction method to study the high reliable star pattern recognition methods, and explore the star pattern recognition optical implementations specific tasks include: 1. based on a comprehensive review of the course of development and research status of the star sensor, star sensor error model analysis of star point extraction and star pattern recognition affect the relationship between the accuracy of the star sensor, the the extracted star point star pattern recognition research status and method of review and analysis. System Star point extraction accuracy of the mechanism and error model. Frequency domain analysis methods, sampling frequency limits and sampling window limits, the theoretical analysis of the system star point system error extraction algorithm to obtain the analytical expression like point the centroid positioning system error, given the star point extraction system error and as the radius of the point Gaussian image point in the coordinate position of the imaging device and the sampling window pixel quantities function relationship. 3 star point extraction error model based on the high accuracy centroid the compensation Star point extraction algorithm. Simulation results show that this method can be basically eliminated the star point extraction system error. Cramér-Rao lower limit of the photon shot noise conditions under the center of mass of the star point positioning error estimation theory, statistical signal processing point, as the standard of the proposed algorithm was evaluated in performance under noisy conditions. The simulation results show that the star point extraction error by the the centroid 1/50 in 1000 photoelectron reduced to nearly 1/100 pixel image. For the practical application of the mutual influence between pixel the additive noise impact and multidimensional promotion algorithm are analyzed and discussed. And through high-precision star point extraction experiments verify the above conclusion. 4. Analysis of the physical limits of the measurement accuracy of star sensor attitude. From the photon shot noise, the Cramér-Rao lower limit to the star point extraction error based on analysis of the physical limits of the measurement accuracy of star sensor attitude. The results show that currently the typical design parameters under the conditions of the star sensor the posture measurement accuracy limit conservative estimate of the value of 0.02, an order of magnitude higher than the current high-precision star sensor there is a large potential for high-precision star sensor. sky star map identification method based on Fourier transform correlation through the analysis of high-precision star sensor for the specific requirements of the star pattern recognition, research the number of the number of the NAVSTAR library star point star point of star maps, star, does not determine the error and error star point extraction mechanism. traditional star pattern recognition method proposed day star pattern recognition method based on Fourier transform correlation, and effectively improve the recognition success rate of the star map, reduce false recognition rate, while not sensitive to to extract error of uncertain magnitude error and the star point. Simulation results show that the identification method in magnitude uncertainty error of 0.4 stars, star point extraction error of 1 pixel conditions recognition success rate can be increased to 99.93% 6 star pattern recognition method based on optical studies by optical joint transform correlator star chart to identify the most time-consuming computation link can be sky star map recognition time is reduced to 80 milliseconds. effective solution to the Star Figure recognition speed. proposed coaxial optical joint transform correlator optical path design, study the diaryl-based optical correlator to reduce the volume of the optical correlator. established star point extraction through this thesis work, system error model and noise impact model proposed high-precision the centroid Compensation Star point extraction algorithm based on Fourier transform the related recognition throughout the day star pattern recognition algorithm and its optical correlation implementations, and simulation and experimental verification, effectively improve the recognition rate of star point extraction accuracy star chart. thesis results next step in the development of high-precision star sensor error of the theoretical basis for the software design of the system design and the critical device parameters selection, as well as high-precision algorithm provides important guidance.