Observation and Modelling of Meter-Class Earth impacting Asteroids
Abstract
Earth is constantly bombarded by solar system objects of a wide variety of sizes, from micron-sized meteoroid stream and sporadic meteor dust, to meter-sized and larger meteoroids observed as fireballs. Fireball event characteristics directly point to the properties and structure of the parent body from which the meteoroid originated. In-atmosphere fireball data paired with in-space observations bring much context to both observations. This thesis centres on three published papers that grew out of my Masters project to identify precovery in-space images of meteoroids first observed as fireballs.
The first article describes the first successful identification of an in-space image of such a pre-fireball meteoroid, a US Government Sensor (USG) detection of an estimated 0.14 kiloton event in September 2020 over the Pacific Ocean. Analysis of the object's on-image streak along with USG, Geostationary Lightening Mapper (GLM), and infrasound observations allow us to characterize the object as a 2-3 meter diameter object of unusually low albedo and fragile structure, comparable to the 2008 TC3 Almahata Sitta impactor.
The second article presents an observing plan for an observationally favourable 2019 passage of a conjectured swarm of sub-kilometre diameter objects associated with the Taurid meteoroid stream. A confirmed Taurid Swarm (TS) would pose significant and continual risk to Earth. Observations of the proposed location of the TS will provide either verification or refutation of the swarm’s existence, and if found, for a determination of the risk presented.
The third article describes the second ever (at the time) observation of a Temporarily Captured Orbiter (TCO). In January 2014 the European Fireball Network observed a fireball event having the slowest ever recorded entry speed. Integrating the object's contact state back in time with the goal to identify precovery images, we discovered the object had made a close pass by the Moon, perturbing the object into an Earth impact from a prior somewhat chaotic low-speed Earth orbit.
The thesis concludes with four appendices describing the precovery image search process, a related work to identify parent bodies of fireball objects, modelling of meteoroid stream evolution, and a brief description of the software ClearSky used to implement these projects.