Ephemeris and hazard assessment for near-Earth asteroid (101955) Bennu based on OSIRIS-REx data
Ephemeris and hazard assessment for near-Earth asteroid (101955) Bennu based on OSIRIS-REx data
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DOI：
10.1016/j.icarus.2021.114594
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发表时间：
2021-09-01
期刊：
影响因子：
3.2
通讯作者：
Lauretta, Dante S.
中科院分区：
文献类型：
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作者：
Farnocchia, Davide;Chesley, Steven R.;Lauretta, Dante S.
小天体，如近地小行星Bennu，由于热辐射力（雅科夫斯基效应）而在轨道上漂移。地面观测表明，贝努撞击地球的可能性不为零，这取决于它的轨道如何演变。因此，前往本努的OSIRIS-REx（起源、光谱解释、资源识别和安全-风化层探测器）使命的目标之一是精确测量亚尔科夫斯基效应，并改进对该天体的撞击危险评估。我们在这里讨论这些目标。利用OSIRIS-REx航天器跟踪数据，我们得出了2019年1月至2020年10月地球与Bennu之间距离的米级约束。虽然这些数据极大地改善了对Bennu轨道的了解，但它们也需要对小行星轨道建模的前所未有的保真度。特别是，需要特别注意考虑到343个小天体扰动的贡献及其质量的不确定性。辐射效应，如坡印廷-罗伯逊阻力，迄今为止只考虑行星际尘埃动力学，现在成为一个考虑建模的500米小行星，如Bennu的轨迹。通过采用基于OSIRIS-REx的Bennu特征的热物理模型，我们估计在2011年1月1日由Yarkovsky效应引起的半长轴漂移为-284.6 +/- 0.2 m/年（信噪比类似于1400）。模型误差的最大来源是太阳风阻力，这可能会降低雅科夫斯基效应的半长轴漂移幅度高达0.16米/年。在1900年至2135年期间，由于行星摄动的影响，贝努的轨道演变，与雅科夫斯基有关的半长轴漂移大约为+1米/年。Yarkovsky热物理模型被证明是非常准确的，通过重力科学分析预测的体积密度估计值在0.1%以内。与OSIRIS-REx使命之前可用的信息相比，对2135年发生的散射地球遭遇情况的了解提高了20倍，从而使我们能够排除许多以前可能的撞击轨迹。然而，仍然有一些撞击轨迹与数据兼容。在航天器相遇之前，到2200年的总体撞击概率为3.7 x 10（-4）（2700分之一）。作为我们分析的结果，到2300年的累积影响概率为5.7 x 10（-4）（1/1750），最重要的单个影响解决方案是2182年9月，影响概率为3.7 x 10（-4）（1/2700）。Bennu和（29075）1950 DA的巴勒莫标度值都是-1.42，是目前小行星目录中最危险的天体。
Small bodies such as the near-Earth asteroid Bennu drift in their orbit due to thermal radiation forces (the Yarkovsky effect). Ground-based observations have indicated a nonzero probability of Bennu impacting Earth, depending on how its orbit evolves. Thus, among the goals of the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) mission to Bennu were to precisely measure the Yarkovsky effect and refine the impact hazard assessment for this body. Here we address these objectives. Using OSIRIS-REx spacecraft tracking data, we derive meter-level constraints on the distance between Earth and Bennu from January 2019 to October 2020. While these data greatly improve the knowledge of the trajectory of Bennu, they also require an unprecedented fidelity for the modeling of an asteroid's trajectory. In particular, special care is needed to take into account the contribution of 343 small-body perturbers and the uncertainty in their masses. Radiation effects such as the Poynting-Robertson drag, so far only considered for interplanetary dust dynamics, now become a consideration for modeling the trajectory of a 500-m asteroid such as Bennu. By employing a thermophysical model based on OSIRIS-REx's characterization of Bennu, we estimate a semimajor axis drift of -284.6 +/- 0.2 m/yr (signal-to-noise ratio similar to 1400) at epoch 2011 January 1 caused by the Yarkovsky effect. The largest source of modeling error is solar wind drag, which may lower the magnitude of the semimajor axis drift from the Yarkovsky effect by up to 0.16 m/yr. The Yarkovsky-related semimajor axis drift varies by roughly +1 m/yr as the orbit of Bennu evolves due to planetary perturbations from 1900 to 2135. The Yarkovsky thermophysical model proves to be extremely accurate by predicting a bulk density estimate within 0.1% of that estimated through gravity science analysis. Compared to the information available before the OSIRIS-REx mission, the knowledge of the circumstances of the scattering Earth encounter that will occur in 2135 improves by a factor of 20, thus allowing us to rule out many previously possible impact trajectories. However, there remain some impact trajectories compatible with the data. Prior to the spacecraft encounter, the overall impact probability through 2200 was 3.7 x 10(-4) (1 in 2700). As a result of our analysis, the cumulative impact probability through 2300 becomes 5.7 x 10(-4) (1 in 1750) and the most significant individual impact solution is for September 2182, with an impact probability of 3.7 x 10(-4) (1 in 2700). Both Bennu and (29075) 1950 DA have a Palermo scale value of -1.42 and share the distinction as the currently most hazardous object in the asteroid catalog.