A Novel Star Identification Method Assisted by Stellar Brightness for Star Tracker

In modern deep space exploration missions, star trackers are crucial attitude determination equipment, which establish the positioning of spacecraft by capturing stars. With the advancement of multi-heads star tracker technology, its designs are increasingly geared towards achieving higher pixel resolution, smaller fields of view (FOV), and the ability to detect fainter stars. However, this development trend inevitably leads to an increase in the number of navigation stars in the field of view, thus challenging the applicability of existing star identification methods. For this, this paper develops a novel star identification method assisted by stellar brightness. This method first establishes a set of magnitude screening criteria and establishes the corresponding relationship between star brightness and apparent magnitude in the star image. Subsequently, stars within the filtering range are prioritized for identification based on stellar brightness and angular distance information. On this basis, the identification process is extended to the stars outside the screening range, and both stages are verified with the help of the directed-loop method to improve the accuracy. Taking the dual-head star tracker of the Gaofen-7 satellite as an example, this method's identification accuracy and attitude determination precision were analyzed by processing its multi-orbit star image data. The results demonstrate that the method not only has a high identification rate but also improves the attitude precision by 0.05 to 0.1 arc seconds compared to telemetry downlinked data. The method proposed in this study provides strong theoretical support for the technological development of future multi-heads star trackers and has potential for practical application.