星敏感器自主在轨校准
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0091-3286/2011/$25.00 C 2011 SPIE
temperature effects, act as systematic errors and change the camera parameters on orbit.8,9 In order to achieve high accuracy for attitude estimations, the systematic errors should be corrected in real time while on orbit. Therefore, the on-orbit calibration is necessary for the aim of higher accuracy.
Jiong-qi Wang National University of Defense Technology College of Science Department of Mathematics and System Science Changsha, Hunan, 410073 China
Ji-chun Tan National University of Defense Technology Institute of Engineering Physics College of Science Changsha, Hunan, 410073 China
(i.e., attitude dependent and attitude independent, respectively) have been proposed. In the attitude-dependent approach, the principal point and the focal length are determined by projecting the inertial cataloged star vectors into the star tracker frame whose attitude is calibrated with gyros or landmark.12,13 However, the error of the star tracker frame attitude affects the calibration inevitably. Thus, the attitudeindependent approach is developed, and it has been indicated that the attitude-independent approach performs better than the attitude-dependent approach, because the latter depends on the camera calibration parameters whereas the former does not.12 Many attitude-independent algorithms have been proposed to estimate the camera parameters by directly utilizing the star coordinate in image plane and corresponding star vector in inertial coordinate frame.14,15 In these methods, the attitude matrix and camera parameters are calculated from a single image, and the optimal solution of camera parameters is obtained from the global optimization of multiple images. Generally, the simple first-order radial distortion model is adopted to reduce computation work. Moreover, the large amount of information for the batch solution is problematic for onboard implementation because spacecraft most likely do not possess the storage capacity and the computational power.
Paper 100559R received Jul. 12, 2010; revised manuscript received Dec. 8, 2010; accepted for publication Dec. 27, 2010; published online Feb. 28, 2011.
The standard calibration procedure is to acquire images of an artificial object with known Euclidean structure and estimate the internal parameters and the external parameters using iterative nonlinear optimization approach and two-step method, in which the distortion is removed in the initial step and then the least squares are performed to minimize the residual.10,11 However, such calibration methods might be problematic to be implemented on-orbit because it is difficult to set up the optical system with an artificial object. Furthermore, the computation work of the iterative nonlinear optimization approach is so complicated and huge that it is difficult for onboard implementation.
Abstract. We have developed a calibration approach for a star tracker camera. A modified version of the least-squares iteration algorithm combining Kalman filter is put forward, which allows for autonomous on-orbit calibration of the star tracker camera even with nonlinear camera distortions. In the calibration approach, the optimal principal point and focal length are achieved at first via the modified algorithm, and then the highorder focal-plane distortions are estimated using the solution of the first step. To validate this proposed calibration approach, the real star catalog and synthetic attitude data are adopted to test its performance. The test results have demonstrated the proposed approach performs well in terms of accuracy, robustness, and performance. It can satisfy the autonomous on-orbit calibration of the star tracker camera. C 2011 Society of Photo-Optical
Hui Jia Xiu-jian Li National University of Defense Technology Institute of Engineering Physics College of Science Changsha, Hunan, 410073 China E-mail: xjli@nudt.edu.cn
Jian-kun Yang National University of Defense Technology Institute of Engineering Physics College of Science Changsha, Hunan, 410073 China and National Laboratory of Space Intelligent Control Beijing, 100190 China
In order to perform on-orbit calibration for the star tracker camera efficiently, two distinct types of approach
Optical Engineering
023604-1
February 2011/Vol. 50(2)
Downloaded from SPIE Digital Library on 06 Mar 2011 to 222.240.177.34. Terms of Use: http://spiedl.org/terms
Liu et al.: Autonomous on-orbit calibration of a star tracker camera
Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3542039]
Subject terms: star tracker; autonomous calibration; kalman filter; interstar angles; distortion.
Optical Engineering 50(2), 023604 (February 2011)
Autonomous on-orbit calibration of a star tracker camera
Hai-bo Liu National University of Defense Technology Institute of Engineering Physics College of Science Changsha, Hunan, 410073 China
wenku.baidu.com
1 Introduction
The autonomous star trackers utilizing star observations are key optoelectronic instruments to provide absolute three-axis attitude for a spacecraft.1 The observable stars within the field of view (FOV) of the star tracker can be identified by several robust algorithms2,3 to achieve the inertial cataloged vectors, which then is compared to the direction vectors in the star tracker reference to estimate the attitude matrix.4,5 The attitude estimation accuracy highly depends on the accuracy of the star camera’s optical parameters, including the focal length f, the principal point (x0, y0), and the focalplane distortions, which are used to represent the star direction vector in the star tracker reference. Generally, the star tracker’s optical parameters are provided by ground-based initial calibration.6,7 However, many factors, such as intense vibration in the process of launching, instrument aging, and
temperature effects, act as systematic errors and change the camera parameters on orbit.8,9 In order to achieve high accuracy for attitude estimations, the systematic errors should be corrected in real time while on orbit. Therefore, the on-orbit calibration is necessary for the aim of higher accuracy.
Jiong-qi Wang National University of Defense Technology College of Science Department of Mathematics and System Science Changsha, Hunan, 410073 China
Ji-chun Tan National University of Defense Technology Institute of Engineering Physics College of Science Changsha, Hunan, 410073 China
(i.e., attitude dependent and attitude independent, respectively) have been proposed. In the attitude-dependent approach, the principal point and the focal length are determined by projecting the inertial cataloged star vectors into the star tracker frame whose attitude is calibrated with gyros or landmark.12,13 However, the error of the star tracker frame attitude affects the calibration inevitably. Thus, the attitudeindependent approach is developed, and it has been indicated that the attitude-independent approach performs better than the attitude-dependent approach, because the latter depends on the camera calibration parameters whereas the former does not.12 Many attitude-independent algorithms have been proposed to estimate the camera parameters by directly utilizing the star coordinate in image plane and corresponding star vector in inertial coordinate frame.14,15 In these methods, the attitude matrix and camera parameters are calculated from a single image, and the optimal solution of camera parameters is obtained from the global optimization of multiple images. Generally, the simple first-order radial distortion model is adopted to reduce computation work. Moreover, the large amount of information for the batch solution is problematic for onboard implementation because spacecraft most likely do not possess the storage capacity and the computational power.
Paper 100559R received Jul. 12, 2010; revised manuscript received Dec. 8, 2010; accepted for publication Dec. 27, 2010; published online Feb. 28, 2011.
The standard calibration procedure is to acquire images of an artificial object with known Euclidean structure and estimate the internal parameters and the external parameters using iterative nonlinear optimization approach and two-step method, in which the distortion is removed in the initial step and then the least squares are performed to minimize the residual.10,11 However, such calibration methods might be problematic to be implemented on-orbit because it is difficult to set up the optical system with an artificial object. Furthermore, the computation work of the iterative nonlinear optimization approach is so complicated and huge that it is difficult for onboard implementation.
Abstract. We have developed a calibration approach for a star tracker camera. A modified version of the least-squares iteration algorithm combining Kalman filter is put forward, which allows for autonomous on-orbit calibration of the star tracker camera even with nonlinear camera distortions. In the calibration approach, the optimal principal point and focal length are achieved at first via the modified algorithm, and then the highorder focal-plane distortions are estimated using the solution of the first step. To validate this proposed calibration approach, the real star catalog and synthetic attitude data are adopted to test its performance. The test results have demonstrated the proposed approach performs well in terms of accuracy, robustness, and performance. It can satisfy the autonomous on-orbit calibration of the star tracker camera. C 2011 Society of Photo-Optical
Hui Jia Xiu-jian Li National University of Defense Technology Institute of Engineering Physics College of Science Changsha, Hunan, 410073 China E-mail: xjli@nudt.edu.cn
Jian-kun Yang National University of Defense Technology Institute of Engineering Physics College of Science Changsha, Hunan, 410073 China and National Laboratory of Space Intelligent Control Beijing, 100190 China
In order to perform on-orbit calibration for the star tracker camera efficiently, two distinct types of approach
Optical Engineering
023604-1
February 2011/Vol. 50(2)
Downloaded from SPIE Digital Library on 06 Mar 2011 to 222.240.177.34. Terms of Use: http://spiedl.org/terms
Liu et al.: Autonomous on-orbit calibration of a star tracker camera
Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3542039]
Subject terms: star tracker; autonomous calibration; kalman filter; interstar angles; distortion.
Optical Engineering 50(2), 023604 (February 2011)
Autonomous on-orbit calibration of a star tracker camera
Hai-bo Liu National University of Defense Technology Institute of Engineering Physics College of Science Changsha, Hunan, 410073 China
wenku.baidu.com
1 Introduction
The autonomous star trackers utilizing star observations are key optoelectronic instruments to provide absolute three-axis attitude for a spacecraft.1 The observable stars within the field of view (FOV) of the star tracker can be identified by several robust algorithms2,3 to achieve the inertial cataloged vectors, which then is compared to the direction vectors in the star tracker reference to estimate the attitude matrix.4,5 The attitude estimation accuracy highly depends on the accuracy of the star camera’s optical parameters, including the focal length f, the principal point (x0, y0), and the focalplane distortions, which are used to represent the star direction vector in the star tracker reference. Generally, the star tracker’s optical parameters are provided by ground-based initial calibration.6,7 However, many factors, such as intense vibration in the process of launching, instrument aging, and