Star selection strategy using measurement coupling matrix in starlight Doppler-based integrated navigation system

The starlight Doppler navigation must be integrated with other navigation methods to operate normally since it is not completely observable. The star selection for the Doppler navigation system influences the whole integrated navigation performance greatly. The star magnitude-based star selection method is commonly used to select the star for the Doppler navigation. However, it can be found that the direction of star is more important than the measurement accuracy. To select the optimal navigation star, the star selection strategy for the starlight Doppler-based integrated navigation system, where both the direction and magnitude of star are considered, is proposed in this paper. Considering the impact of the star direction and measurement noise, the measurement coupling matrix is constructed to give the relationship between the star direction and the integrated navigation accuracy, and utilize this matrix as the star selection criterion. According to the perturbation matrix theory, the measurement coupling matrix is analyzed to obtain the theoretical maximum and minimum of its trace by formula derivation. Finally, the proposed star selection criterion is utilized to select the optimal navigation star from the first-magnitude stars. In this paper, the XNAV (X-ray pulsar navigation)/starlight Doppler integrated navigation system is taken as an instance to analyze and simulate. The simulation results demonstrate that using the star selected by our method as the navigation star, the XNAV/starlight Doppler integrated navigation has good performance. Compared with the X-ray sensor area and the spectrometer measurement accuracy, the direction of star is more important for the improvement of the integrated navigation performance.