Observational studies of small solar system bodies: origins, dynamics and structure

太阳系中的小天体（小行星、彗星、半人马和海王星外天体）是太阳系形成阶段的遗迹。在许多情况下，它们含有未经实质性加工的原始材料。它们的物理结构，化学和动力学演化为早期太阳系提供了一个独特的窗口，为我们的太阳系和其他行星系统的形成模型提供了信息。 这些天体的碎片偶尔会撞击地球大气层，产生电离、辐射和“流星”形式的冲击。通过研究碎片（流星体）如何在大气层中烧蚀，我们可以重建其特性（体积密度、强度、粒度），进而了解其母体。 该建议的方法是通过记录流星体的光、电离和冲击波的产生，观测其大小从尘埃颗粒到巨石等与大气层相互作用的流星体。通过测量它们的质量和各种大小的数量，我将准确地估计这些天体到地球的流量。对于较小的流星体，这将有助于提炼地球积累的陨石物质。对于更大的物体（米-十进制），我将测量它们的冲击效果，特别是冲击强度，因为这对限制火球如何在地面造成破坏至关重要。在2015年2月15日俄罗斯车里雅宾斯克空中爆炸之后，迫切需要更好的地面损伤模型，以帮助通知民防官员，以防在撞击前检测到另一个数米大小的近地物体。对于这些较大的事件，陨石的回收也提供了“地面实况”的前身体的组成和结构。如果我们能够同时记录大气中的火球，那么这种较大的撞击物也构成了进入模型的最终校准。通过对各种大小的大气中的碎裂行为进行建模，我将测量大量流星体的强度和体积密度，并将其与撞击前的轨道相关联。其结果将是一个详细的协调一致的图片的强度/结构和轨道起源的尘埃到巨石大小的物体与地球碰撞。最终，这将从尘埃和较大的近地天体两个方面，对近地空间小型天体的起源和目前的生态情况形成一个了解。由此得出的关于地球附近尘埃到巨石大小流星体的数量和物理特性的“路线图”，对于行星防御和保护航天器不受流星体撞击具有实际重要性。即将到来的航天器任务也需要这些信息，例如NASA的小行星重定向使命，该任务旨在将一块巨石大小的岩石从近地小行星送回月球轨道。

The small bodies in the solar system (asteroids, comets, centaurs and trans-Neptunian objects) are relics from the formation stage of our solar system. In many cases they contain primitive material which has not experienced substantial processing. Their physical structure, chemistry and dynamical evolution offer a unique window into the early solar system informing formation models of our solar system and other planetary systems. Fragments of these bodies occasionally impact the Earth’s atmosphere, producing ionization, radiation and shocks in the form of “meteors”. By studying how the fragment (meteoroid) ablates in the atmosphere we can reconstruct its properties (bulk density, strength, grain sizes) and by extension learn about its parent body. The approach of this proposal is to observe meteoroids ranging in size from dust grains to boulders interacting with the atmosphere by recording their light, ionization and shock production. By measuring their mass and numbers at all sizes I will accurately estimate the flux of these bodies to Earth. For smaller meteoroids this will help in refining the amount of meteoritic material accumulated by the Earth. For larger objects (meter-decameter-scale) I will measure their impact effects, particularly shock strength, as this is critical to constraining how fireballs can cause damage at the ground. In the wake of the Feb 15, 2015 Chelyabinsk airburst over Russia there is a pressing need for better ground damage models to help inform civil defence officials in the event another multi-meter sized near-Earth object is detected just prior to impact. For these larger events, recovery of meteorites also provides “ground-truth” for precursor body composition and structure. Such larger impactors also form the ultimate calibration for entry models, if we are able to simultaneously document the fireball in the atmosphere. Through modelling of the breakup behavior in the atmosphere at all sizes I will measure the strength and bulk density of a large number of meteoroids and correlate this with their pre-impact orbits. The result will be a detailed coordinated picture of the strength/structure and orbital origins for dust-to-boulder sized objects colliding with the Earth. Ultimately this will build up a picture of the origins and present ecology of small bodies in near-Earth space both in terms of dust and larger Near-Earth Objects (NEOs). The resulting “road-map” of the number and physical characteristics of dust to boulder sized meteoroids near Earth is of practical importance for planetary defence and for the protection of spacecraft from meteoroid impacts. This information is also needed for upcoming spacecraft missions such as the NASA Asteroid Redirect Mission, which seeks to return a boulder-sized rock to lunar orbit from a near-Earth asteroid.