Hayabusa2 is the Japanese Asteroid Return Mission and targeted the carbonaceous asteroid Ryugu, conducted by the Japan Aerospace Exploration Agency (JAXA). The goal of this mission was to conduct proximity operations including remote sensing observations, material sampling, and a Small Carry-On Impact experiment, as well as sample analyses. As of September 2020, the spacecraft is on the way back to Earth with samples from Ryugu with no critical issues after the successful departure in November 2019. Here, we propose an extended mission in which the spacecraft will rendezvous with a small asteroid with ~30 m - ~40 m in diameter that is rotating at a spin period of ~10 min after an additional ~10-year cruise phase. We introduce that two scenarios are suitable for the extended mission. In the first scenario, the spacecraft will perform swing-by maneuvers at Venus once and Earth twice to arrive at asteroid 2001 AV43. In the second scenario, it will perform swing-by maneuvers at Earth twice to reach asteroid 1998 KY26. In both scenarios, the mission will continue until the early 2030s. JAXA recently released the decision that the spacecraft will rendezvous with 1998 KY26. This paper focuses on our scientific assessments of the two scenarios but leaves the decision process to go to 1998 KY26 for future reports. Rendezvous operations will be planned to detail the physical properties and surrounding environments of the target, one of the smallest elements of small planetary bodies. By achieving the planned operations, the mission will provide critical hints on the violent histories of collisions and accumulations of small bodies in the solar system. Furthermore, the established scientific knowledge and techniques will advance key technologies for planetary defense.

Hayabusa2 是日本小行星返回任务，目标是碳质小行星 Ryugu，由日本宇宙航空研究开发机构 (JAXA) 执行。该任务的目标是进行近距离操作，包括遥感观测、材料采样、小型随身携带影响实验以及样本分析。截至 2020 年 9 月，该航天器正在返回地球，并在 2019 年 11 月成功离开后携带来自龙宫的样本返回地球，没有出现严重问题。在这里，我们提出一项扩展任务，其中航天器将与一颗约 30 m - 直径约 40 m，在额外的约 10 年巡航阶段后以约 10 分钟的自旋周期旋转。我们介绍两种场景适用于扩展任务。在第一个场景中，该航天器将在金星和地球上执行一次摆动机动，以到达小行星 2001 AV43。在第二种情况下，它将在地球上执行两次摆动机动以到达小行星 1998 KY26。在这两种情况下，任务都将持续到 2030 年代初。JAXA 最近发布了航天器将与 1998 KY26 会合的决定。本文侧重于我们对这两种情景的科学评估，但将决策过程留给 1998 KY26 以供将来报告。将计划进行交会行动，以详细说明目标的物理特性和周围环境，目标是小行星体中最小的元素之一。通过实现计划中的操作，该任务将提供有关太阳系中小天体碰撞和堆积的剧烈历史的重要线索。