Achievement of the Planetary Defense Investigations of the Double Asteroid Redirection Test (DART) Mission

NASA’s Double Asteroid Redirection Test (DART) mission was the first to demonstrate asteroid deflection, and the mission’s Level 1 requirements guided its planetary defense investigations. Here we summarize DART’s achievement of those requirements. On 2022 September 26, the DART spacecraft impacted Dimorphos, the secondary member of the Didymos near-Earth asteroid binary system, demonstrating an autonomously navigated kinetic impact into an asteroid with limited prior knowledge for planetary defense. Months of subsequent Earth-based observations showed that the binary orbital period was changed by –33.24 min, with two independent analysis methods each reporting 1-σ uncertainties <2 s. Dynamical models determined that the momentum enhancement factor, β, resulting from DART’s kinetic impact test is between 2.4 and 4.9, depending on the mass of Dimorphos, which remains the largest source of uncertainty. Over five dozen telescopes across the globe and in space, along with the Light Italian CubeSat for Imaging of Asteroids (LICIACube), have contributed to DART’s investigations. These combined investigations have addressed topics related to the ejecta, dynamics, impact event, and properties of both asteroids in the binary system. One year following DART’s successful impact into Dimorphos, the mission has achieved its planetary defense requirements, though work to further understand DART’s kinetic impact test and the Didymos system will continue. In particular, ESA’s Hera mission is planned to perform extensive measurements in 2027 during its rendezvous with the Didymos-Dimorphos system, building on DART to advance our knowledge and continue the ongoing international collaboration for planetary defense.

美国国家航空航天局（National Aeronautics and Space Administration, NASA）的双小行星重定向测试（Double Asteroid Redirection Test, DART）任务是全球首个实现小行星偏转技术演示的航天任务，该任务的一级（Level 1）需求为其行星防御相关研究提供了核心指引。本文总结了DART任务达成上述各项需求的具体成果。2022年9月26日，DART航天器撞击了近地双小行星系统迪迪莫斯（Didymos）的次级天体迪摩弗斯（Dimorphos），成功演示了在仅具备有限先验知识的前提下，通过自主导航完成动能撞击小行星的行星防御技术验证。后续数月的地面观测数据显示，该双星系统的轨道周期缩短了33.24分钟，两种独立分析方法给出的1σ不确定度均小于2秒。动力学模型测算结果表明，DART动能撞击试验产生的动量增强因子β介于2.4至4.9之间，具体数值取决于迪摩弗斯的质量——这仍是当前研究中最大的不确定性来源。全球及在轨部署的六十余台望远镜，搭配意大利小行星成像小型立方体卫星（Light Italian CubeSat for Imaging of Asteroids, LICIACube），均为DART的相关研究提供了观测支持。上述多源综合研究覆盖了撞击喷流动力学、撞击事件特性以及该双星系统中两颗小行星的物理属性等相关议题。在DART成功撞击迪摩弗斯一周年之际，该任务已圆满达成其预设的行星防御相关需求，但针对DART动能撞击试验及迪迪莫斯系统的后续研究仍将持续推进。尤为值得关注的是，欧洲空间局（European Space Agency, ESA）的赫拉（Hera）任务计划于2027年与迪迪莫斯-迪摩弗斯系统交会，开展全面的高精度测量工作，以DART任务为基础深化人类对该系统的认知，并持续推进全球行星防御领域的国际合作。