Design and Reconstruction of the Hayabusa2 Precision Landing on Ryugu

This research focuses on the design and reconstruction of the first touchdown of Hayabusa2 on the asteroid Ryugu. Because of the plethora of boulders, the landing operation required high accuracy to ensure spacecraft safety. This paper therefore investigates a pinpoint touchdown sequence using a retroreflective marker as an artificial landmark. First, the dynamical environment in the vicinity of Ryugu is explored for precise trajectory analyses; particularly, the irregular gravitational field around Ryugu is computed, which has an impact on the spacecraft motion. Based on the dynamics model, the touchdown trajectory used to land on the selected landing site with a radius of 2.8 m is designed. This process is followed by landing dispersion analyses, validating the feasibility of the touchdown sequence. As a result, the Hayabusa2 spacecraft successfully landed on the asteroid Ryugu on 21 February 2019. This paper further provides trajectory reconstruction results based on actual flight data, revealing that the achieved landing accuracy was 1 m. Consequently, this work demonstrates the performance of the proposed precision landing strategy and expands the capabilities of small-body missions.