Abstract: For the close-proximity exploration mission of small-sized asteroids, the search methods for dawn-dusk orbits near asteroids and the influencing factors of their stability were investigated. A high-precision dynamical model was established, which comprehensively considers the asteroid’s irregular gravity, solar radiation pressure, and solar gravitational perturbations. Based on the Sequential Quadratic Programming (SQP) algorithm, an optimization model was developed, focusing on the long-term stability of the orbital semi-major axis. This model was used to search for stable dawn-dusk orbits near the asteroid, and the impact of different conditions on orbital stability was analyzed. Numerical simulations successfully identified stable dawn-dusk orbit families for 30-meter-sized asteroids. The distribution of these orbits aligned with the theoretical balance point trend, validating the effectiveness of the approach. The analysis of different conditions showed that decreasing density and size, as well as increased rotation speed, led to lower orbital stability. The inclination of the rotation axis significantly influenced stability, though no monotonic pattern was observed. Among four typical asteroid shapes, near-spherical asteroids had smaller minimum stable orbital semi-major axes and higher stability, while dumbbell-shaped asteroids exhibited the opposite trend.The high-precision dynamical model and streamlined optimization method are effective for searching and analyzing dawn-dusk orbits in the gravitational fields of irregular asteroids under strong perturbations. These methods offer high practical applicability, and the analysis of various influencing factors provides valuable qualitative insights for future reconnaissance missions.

Key words: small-sized asteroids, orbit design, dawn-dusk orbit, orbit stability