Abstract
The integration of a star tracker and gyroscope units (GUs) can take full advantage of the benefits of each, and provide continuous and accurate attitude information with a high update rate. The systematic error calibration of the integrated system is a crucial step to guarantee its attitude accuracy. In this paper, a comprehensive calibration method for the star tracker and GUs integrated system is proposed from a global perspective. Firstly, the observation model of the predicted star centroid error (PSCE) with respect to the systematic errors including the star tracker intrinsic parameter errors, GUs errors and fixed angle errors is accurately established. Then, the systematic errors are modeled by a series of differential equations, based on which the state-space model is established. Finally, the systematic errors are decoupled and estimated by a Kalman filter according to the established state-space model and observation model. The coupling between the errors of the principal point and subcomponents of the fixed angles (i.e., and ) is analysed. Both simulations and experiments indicate that the proposed method is effective at estimating the systematic errors of the star tracker and GUs integrated system with high accuracy and robustness with respect to different star centroid accuracies and gyroscope noise levels.
Highlights
Since the predicted star centroid error (PSCE) is induced by the systematic errors of the star tracker and gyroscope units (GUs) integrated system, these errors can be estimated by observing the PSCE
We have shown that a star tracker and GUs can be used together to take full advantage of the benefits of each
Existing calibration methods mainly focus on the single star tracker, and separate calibrations of the star tracker and GUs increase the complexity of the calibration process
Summary
A star tracker, which can provide high-accuracy attitude information with respect to an inertial frame [1,2,3,4], has been widely used in the fields of attitude determination, guidance and navigation [5,6,7]. The star tracker and GUs integrated system can take advantage of the benefits of each and has the potential to provide continuous, highly accurate attitude information with high update rate. The on-orbit calibration method based on the invariance of the interstar angle [16] was first proposed by Samaan et al Due to the attitude-independent characteristics, this method is the most widely used on-orbit calibration approach It was developed by many researchers in terms of the parameter estimation algorithms and improvements to the measurement model. We propose a comprehensive calibration method for a star tracker and GUs integrated system from a global perspective. A Kalman filter can be used to estimate these systematic errors optimally with the established state-space model and observation model, the performance of the integrated system can be improved.
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