Design of Two-Impulse Soft-Landing Trajectories From Unstable Periodic Orbits Around an Irregular Asteroid by Gravity Model Continuation

The landing trajectory around irregular asteroids has garnered significant attention due to its importance in the asteroid exploration mission, especially if the natural dynamics near the target body is exploited to alleviate tight propellant consumption requirements. Computational closed-loop guidance techniques have provided a reliable generation of the optimal landing trajectories. However, they still require improvements in several aspects. The physical interpretation of the calculation process needs further clarification, and the ability to exploit the complex gravitational fields of irregular asteroids needs further improvement. This article introduces a gravity model continuation method to generate the landing trajectories fast and reliably. The study starts from the landing trajectories with the point-mass model and applies the continuation method to obtain the corresponding landing trajectories with the ellipsoid model and the polyhedron model in sequence. By extending the low-precision model to medium- and high-precision ones gradually, the trajectory generation becomes less complex and more intuitive, and the similarities of landing trajectories with these models are indicated. This method is used to generate landing trajectories starting from periodic orbits around 433 Eros. This demonstrates the impact of the periodic orbit characteristics on the DeltaV and robustness of the landing trajectories and tests the efficiency and feasibility of the gravity model continuation method.