Asteroid (162173) Ryugu is the target object of Hayabusa2, an asteroid exploration and sample return mission led by Japan Aerospace Exploration Agency (JAXA). Ground-based observations indicate that Ryugu is a C-type near-Earth asteroid with a diameter of less than 1 km, but the knowledge of its detailed properties is very limited prior to Hayabusa2 observation. This paper summarizes our best understanding of the physical and dynamical properties of Ryugu based on ground-based remote sensing and theoretical modeling before the Hayabusa2’s arrival at the asteroid. This information is used to construct a design reference model of the asteroid that is used for the formulation of mission operation plans in advance of asteroid arrival. Particular attention is given to the surface properties of Ryugu that are relevant to sample acquisition. This reference model helps readers to appropriately interpret the data that will be directly obtained by Hayabusa2 and promotes scientific studies not only for Ryugu itself and other small bodies but also for the solar system evolution that small bodies shed light on.

中文翻译：

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Hayabusa2遭遇前的小行星Ryugu

小行星（162173）龙ugu是Hayabusa2的目标物体，Hayabusa2是由日本航空航天局（JAXA）领导的小行星探索和样品返回任务。地面观测表明，琉球为直径小于1 km的C型近地小行星，但在Hayabusa2观测之前，其详细性质的知识非常有限。本文总结了我们在summarize鸟2到达小行星之前基于地面遥感和理论建模对龙宫的物理和动力学特性的最佳理解。该信息用于构建小行星的设计参考模型，该模型用于在小行星到达之前制定任务运营计划。特别注意与样品采集有关的Ryugu的表面特性。