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Analysis of Target Marker's Dynamics

Analysis of Target Marker's Dynamics


Hayabusa2 used artificial landmark called Target Marker (TM) as a navigation aid. To mitigate the rebound motion on an asteroid surface, the TM is composed of a shell and hundreds of small balls. Due to the collision among small balls dissipating the energy, rebound motion becomes smaller. We evaluate the rebound mitigation performance and translational motion after the rebound. This study contributes to the design of payloads in asteroid missions.



Although Hayabusa2’s Target Marker (TM) deployment showed that the TM can be deployed and settled under microgravity, the mechanism of the rebound damping is not fully explained. Understanding the rebound mitigation mechanism is necessary to improve the rebound damping performance of new payloads for future small body missions. Therefore, this study elucidates the mechanism of rebound mitigation and proposes an optimal design including the inner balls’ number and radius.
The rebound motion of a TM is simulated by a discrete element method. In addition, we have conducted a microgravity environment experiment in a drop tower. Comparing the result of the experiment and simulations, TM’s rebound performance is evaluated. In addition to the rebound mitigation effect, we consider the translational motion of a TM. We have investigated the shapes that can effectively stop translational motion in a microgravity environment.
The contribution of this study is that we offer the design criteria for a payload to deploy to the asteroid surface in order to prevent unnecessary rebound motion. This study enables a more reliable payload deployment in microgravity environments, resulting in broader options in a proximity phase of a small body mission.