Seminar: Shapes and Spins of Near-Earth Asteroids

Dr Michael Busch

CalTech/UCLA

Asteroids are diverse and numerous solar system objects, from the large number of objects in the main asteroid

belt to the relatively small near-Earth population. Understanding their physical properties is essential to un- derstanding the evolution of the solar system, and asteroid morphology is a complex field in its own right. The histories of individual asteroids, and

particularly near-Earth objects, reflect continuous interaction among their shapes, rotation states, and orbits due to the effects of radiation pressure.

Radar astronomy has provided detailed information on the orbits, sizes, shapes, rotation states, and composition of many asteroids. To improve the capabilities of asteroid radar observations, I have developed the technique of radar speckle tracking. The echoes from different points on the surface of a radar target interfere with each other, producing a pattern of bright and dark speckles across the surface of the Earth. Using radio astronomy techniques, I track the motion of speckles between several ground stations during a radar experiment to accurately determine the rotation state of the target. Speckle tracking is a powerful tool to both determine the orbital evolution of near-Earth asteroids, particularly potential Earth impactors, and to survey the overall physical properties of the asteroid population.