Star identification is a critical technology in the research of star sensors. Conventional star identification algorithms identify stars based only on the geometry position information. As a result, these algorithms are sensitive to positional noise or require a high number of imaged stars in the field of view. In this paper, a star identification algorithm using color ratio information is proposed to solve this problem. An analytical model is developed to predict the performance of the proposed algorithm. In addition, an optimized strategy is proposed to reduce the identification time by selecting stars with the same color ratio information to construct the observation triangles. Experimental results on simulation and real sky images show that the proposed algorithm is robust to high-level position noise, and it requires three stars to find a unique match. Compared with the pyramid algorithm, the proposed algorithm uses fewer stars and achieves a higher star identification rate over the entire sky in a shorter time even under harsh conditions.

This paper presents an image registration method specifically designed for a star sensor equipped with three complementary metal oxide semiconductor (CMOS) detectors. Its purpose is to register the red-, green-, and blue-channel star images acquired from three CMOS detectors, assuring the precision of star image fusion and centroid extraction in subsequent stages. This study starts with a theoretical analysis aimed at investigating the effect of inconsistent three-channel imaging parameters on the position of feature points. Based on this analysis, this paper establishes a registration model for transforming the red- and blue-channel star images into the green channel’s coordinate system. Subsequently, the method estimates model parameters by finding a nonlinear least-squares solution. The experimental results demonstrate the correctness of the theoretical analysis and the proposed registration method. This method can achieve subpixel alignment accuracy in both the x and y directions, thus effectively ensuring the performance of subsequent operation steps in the 3CMOS star sensor.