Abstract
Star sensor needs real-time calibration to improve its navigation accuracy. Compared with other parameters, the position of the principal point is more easily affected by the measurement error, which leads to low calibration accuracy. Conventional star sensors on-orbit calibration methods mainly rely on the angular distance(AD) between stars. The observability of the principal point in this method and the calibration accuracy is not as well as that of other parameters. In this paper, an on-orbit calibration method of star sensor based on the angular distance subtraction(ADS) is proposed. The accuracy of the on-orbit calibration is improved by increasing the observability of the principal point in the calibration process, and the feasibility of this method is verified by the observability analysis. Finally, improved angular distance subtraction(IADS) models are proposed to solve the time-consuming problem of ADS method. In order to demonstrate the performance of the IADS models, simulation calibrations are conducted. The results show that the accuracy of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u<sub>0</sub></i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v<sub>0</sub></i> of the IADS method is 62.7% and 15.9% higher than that of AD method when other parameters are set as nominal values. The calibration accuracy of the principal point is improved effectively.
Highlights
Star sensor is a kind of navigation system and it is the optical attitude sensor with the highest precision at present [1], [2], it has become one of the indispensable navigation equipment on the spacecraft [3], [4]
The results show that the accuracy of u0 and v0 of the IADS method is 62.7% and 15.9% higher than that of angular distance (AD) method when other parameters are set as nominal values
We found that the focal length and distortion parameters calibration of IADS2 method is not as good as AD method and SVD method, but the calibration accuracy of the principal point is still improved
Summary
Star sensor is a kind of navigation system and it is the optical attitude sensor with the highest precision at present [1], [2], it has become one of the indispensable navigation equipment on the spacecraft [3], [4]. It is necessary to calibrate the star sensor parameters on-orbit to improve the working accuracy and autonomous ability. The method of angular distance is widely used, the calibration accuracy of the principal point is much worse than that of other parameters [13], [14]. Nie [17] improved the calibration accuracy by weighting the principal point and focal length, and eliminating the star points with large random measurement noise. The feasibility of this method is verified by observability analysis, and an optimal improved angular distance subtraction(IADS) model is discussed.
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