Shape Modeling and Boulder Mapping of Asteroid 1992 UY4

Speaker: Nicholas Duong, University of Louisville

Abstract: In August 2005, the near-Earth Asteroid 1992 UY4 made a close flyby, coming within 0.04 au of our planet. Between the dates of 1-10 August 2005, it was observed via delay-Doppler radar imaging by the Arecibo Observatory (2380 MHz, 13 cm) and the DSS-14 antenna at the Goldstone Deep Space Communications Complex (8560 MHz, 3.5 cm). The images achieve a resolution as fine as 7.5 m/pixel and reveal a lumpy and modestly asymmetric object. The images also revealed the presence of numerous large boulders/blocks on the surface of 1992 UY4. By using the modeling software SHAPE, I found two potential pole directions: one at ecliptic longitude = 285 deg, latitude = -80 deg and one at long. = 110 deg, lat. = 75 deg, the mirror direction. They represent a north-south ambiguity: UY4 may rotate either prograde or retrograde. I find that the models for the first pole direction better matches the observations and I conclude that UY4 is most likely a retrograde rotator. I also identified 18 boulder candidates on UY4’s surface. With the available data, I cannot determine if boulders are uniformly distributed across the surface of 1992 UY4 or not.