Highly Efficient Attitude-Estimation Algorithm for Star Trackers Using Optimal Image Matching

This paper presents a novel attitude-estimation algorithm for spacecraft using a star tracker. The algorithm is based on an efficient approach to match the stars of two images optimally on top of each other, hence the name of the algorithm: attitude estimation using image matching. In tests, attitude estimation using image matching proved to be as robust as the most robust existing methods, and faster than the fast iterative methods. On top of this, attitude estimation using image matching allows, in a lot of cases, the elimination of a computationally intensive coordinate conversion, which normally precedes the attitude-estimation algorithm. The computational cost of this conversion step is several times higher than that of the attitude-estimation algorithm itself, and so this elimination yields a huge increase in efficiency as compared to the existing algorithms. This significant reduction in computational cost allows to obtain the attitude estimates at a higher rate, implement more accurate centroiding algorithms, or use more stars in the attitude-estimation algorithm, all of which improve the performance of the attitude estimation. It could also allow the use of star trackers in the expanding field of small-satellite projects, in which satellite platforms have a limited computational capability.