Optical system design of star sensor and stray light analysis

Background: Star sensor is one of the precise attitude determination sensors. It is an electro-optical system that takes an image from a set of stars and by comparing it with the star catalogue determines angle deviation of the satellite and modifies its attitude. Star sensor is composed of baffle, optical system, detector, and electronic and image processing system. Methods: In this article, first subsystems of a star sensor is briefly described, then by determining the optical parameters, an optical system with proper quality is designed, and the tolerances are considered. Results: The simulation results and the optical evaluation curves indicate that the image quality is close to the diffraction limit. Next, stray lights from off-axis sources like the sun, are analyzed. For this purpose, the main parameters of baffle designing such as its dimensions and arrangement of the vanes inside it, are determined and then a cylindrical baffle with internal vanes for the star sensor is designed. Conclusion: Results show that stray lights reduced 10-11 times with the presence of baffle and its vanes.