Measuring the Rotational Period of Near Earth Asteroids

1. Measuring the Rotational Period of Near Earth Asteroids Quintin Schiller; University of Wisconsin, Madison Claud H. Sandberg Lacy; University of Arkansas, Fayetteville Motivation Asteroids have been observed for hundreds of years, but only recently has the human species understood the hazard that these objects can represent. Potentially dangerous asteroids, or Near Earth Asteroids (NEAs), cross 1.3 AU from the sun and are candidates for the next extinction level event. In order to prevent such an event, we must determine which NEAs have a high probability for impact and then alter their trajectory outside of impact cross-section. To do so a spacecraft will likely land on the NEA, a mission similar to NASA’s Near Earth Asteroid Rendezvous probe and Japan’s JAXA Hayskusa craft. The maneuver, whether for defense or for scientific interests, requires the rotational period to be known to synchronize the motion of the craft with the object. Purpose I propose to investigate the rotational period of NEAs. Method Step 1: Image asteroid for multiple nights Step 2: Measure magnitude variation with comparison to nearby stars Step 3: Create lightcurve from measurements Step 4: Calculate period of rotation from lightcurve Results After observing Juno for 6 nights, the rotational period was determined to be 0.300452 +/- 0.000001 days. This result is comparable to the published result of 0.3003969 +/- 0.0000003 days1. Lightcurve Phase Diagram Juno 05/30/2007 03:25:18 Juno 05/31/2007 07:34:10 6 Nights of observation 05/30-06/01/2007 Lightcurve of Juno 05/30-05/31/2007 From Here… Juno, unfortunately, is not a Near Earth Asteroid but a main belt asteroid. It was, however, a necessary base to build the experimental procedure. The next step is to select and observe potentially hazardous NEAs. Additional observations could be used to determine the rotational axis angle and morphology of the selected asteroids, from which we could combine trajectory and rotational period to infer its motion through space. Acknowledgements and References 1Birch, P.V.; Taylor, R.C., Lightcurves and Pole Position of Asteroid 3 Juno, A&AS Supplement Series, vol. 81, no. 3, Dec. 1989, p. 409. I would like to thank the NSF for funding the REU program, the Arkansas Center for Space and Planetary Sciences for hosting it, Krista White for providing the photograph of myself, and lastly and mostly, Claud H. S. Lacy for supervising me and writing the programs used for measurements and calculations. Contact Quintin Schiller: qgschiller at wisc.edu