Dr. William Merline and his team will continue and extend their survey for satellites of asteroids, using adaptive optics (AO) on large ground-based telescopes. Their existing project began in 1998, jointly supported by both NSF and NASA. They will continue that arrangement here, but with increased support for analysis, interpretation, and dissemination of results. This new phase of the program will double the number of objects observed so far (to a total of about 1500). The focus will shift to those smaller (and so fainter) asteroids that have eluded observation to date. Continual advances in techniques and technology since the program began mean that these faint objects can now be accessed. Within about the next year, laser-guided AO will become available, giving access to fainter objects. The team recently acquired simultaneous near-IR spectra of an asteroid/satellite pair and they will expand such studies, which will yield taxonomic type and compositional differences (based on near-IR band parameters) and which will help probe the origin of binary systems. Application of the new technique of interferometric nulling should substantially improve the brightness limits for close-in satellites. Deeper searches for satellites near Ceres and Vesta will support the upcoming DAWN spacecraft mission to those asteroids. The team's development of new tools enables prediction of dozens of appulse events per night for many faint asteroids, so that even without laser AO it is possible to observe many small asteroids. The proposed program will focus on main-belt and Trojan targets, but also include near Earth object (NEO) and trans-Neptunian Object (TNO) targets when possible during observing runs planned at Keck, Gemini, VLT, Palomar, and IRTF observatories.
INTELLECTUAL MERIT. Discovery and study of asteroid satellites provides vital information that addresses the specific collisional environment of a particular asteroid and probes the composition and structure of asteroids. Asteroid satellites are critical in two ways: 1) they permit determination of the mass of the primary asteroid, hence its density; density is a prime parameter for any object, whether a wrapped Christmas gift or an asteroid and (except for the largest asteroids and those visited by spacecraft) it cannot be obtained in any other way; and 2) they provide a real-life laboratory for the study of collisions. Collisions have played the dominant role shaping asteroids over the eons and, indeed, most bodies in the solar system. One need only look at the surface of the moon to realize the effects collisions have had on solar system history.
BROADER IMPACT. Asteroids are among the most popular and relevant astronomical targets for lay people in general (mainly because their fragments, meteorites, arrive on Earth as blazing bolides and because there is a tiny but real threat of a devastating impact by a large asteroid). That some asteroids are double or have satellites is one of the most fascinating new facts about solar system bodies in recent years. Thus study of asteroids provides a natural gateway for many into astronomy and the wider world of science. This research program includes an integral component of education and public outreach, to be conducted by scientists who already have a national reputation for excellence and effectiveness in communicating science to the broader society. ***
