Momentum Transfer from the DART Mission Kinetic Impact on Asteroid Dimorphos

Abstract

The NASA Double Asteroid Redirection Test (DART) mission performed a kinetic impact on asteroid Dimorphos, the satellite of the binary asteroid (65803) Didymos, at 23:14 UTC on September 26, 2022 as a planetary defense test1. DART was the first hypervelocity impact experiment on an asteroid at size and velocity scales relevant to planetary defense, intended to validate kinetic impact as a means of asteroid deflection. Here we report the first determination of the momentum transferred to an asteroid by kinetic impact. Based on the change in the binary orbit period2, we find an instantaneous reduction in Dimorphos’s along-track orbital velocity component of 2.70 ± 0.10 mm s–1, indicating enhanced momentum transfer due to recoil from ejecta streams produced by the impact3,4. For a Dimorphos bulk density range of 1,500 to 3,300 kg m–3, we find that the expected value of the momentum enhancement factor, β, ranges between 2.2 and 4.9, depending on the mass of Dimorphos. If Dimorphos and Didymos are assumed to have equal densities of 2,400 kg m–3, 〖β=3.61〗_(-0.25)^(+0.19) (1σ). These β values indicate that significantly more momentum was transferred to Dimorphos from the escaping impact ejecta than was incident with DART. Therefore, the DART kinetic impact was highly effective in deflecting the asteroid Dimorphos.

小行星防御卫星的轨道特性对其防御范围的影响研究

“…末期或 2025 年至 2026 年实现针对某一具有威胁性小 行星的近距离观测和撞击 [8] 。 根据预警时间的不同， 可以将防御措施分为长期 预警时间防御措施和短期预警时间防御措施 [9] 。长期 预警时间防御措施包括使用引力拖车牵引、 改变其受 到的太阳光压力、使用激光侵蚀等，文献 [10][11]等提 出了利用接近小行星的航天器的万有引力来改变小 行星轨道的方法，即引力拖车牵引方法；文献 [12][13][14] 等研究了引力拖车的动力学和控制，而文献 [15 了解 [28][29][30] 。在 2022 年 9 月 26 日的 DART 任务中，美 国宇航局(NASA)对近地双小行星系统 Didymos 中 较小的小行星 Dimorphos 进行了撞击， 以改变其运行 轨道 [31][32] 。 这是世界上首个旨在防御地球免受小行星 撞击威胁的测试任务 [33] 。 可简化为经典的二体问题中的 Lambert 问题 [47][48][49] ，即 根据给定转移时间Δt 以及两个位置矢量 r1、r2，确…”