HR: 08:00h
AN: P31C-01    [Abstracts]
TI: Ceres Observations with HST: Size, Shape, Pole and Rocky Core
AU: * Parker, J
EM: joel@boulder.swri.edu
AF: Southwest Research Institute, Dept. of Space Studies 1050 Walnut St., Boulder, CO 80302 United States
AU: Thomas, P C
EM: thomas@baritone.astro.cornell.edu
AF: Cornell University, 422 Space Sciences Bldg., Ithaca, NY 14853-6801 United States
AU: Young, E F
EM: efy@boulder.swri.edu
AF: Southwest Research Institute, Dept. of Space Studies 1050 Walnut St., Boulder, CO 80302 United States
AU: Sykes, M V
EM: sykes@as.arizona.edu
AF: Planetary Science Institute, 1700 E. Fort Lowell, Ste. 106, Tucson, AZ 85719-2395 United States
AU: McFadden, L
EM: mcfadden@astro.umd.edu
AF: University of Maryland, Depot. of Astronomy, College Park, MD 20742 United States
AU: Russell, C T
EM: ctrussell@igpp.ucla.edu
AF: University of California Los Angeles, Institute of Geophysics and Planetary Physics, 405 Hilgard Ave., Los Angeles, CA 90095-1567 United States
AU: Stern, S A
EM: astern@swri.edu
AF: Southwest Research Institute, Dept. of Space Studies 1050 Walnut St., Boulder, CO 80302 United States
AB: Our team has obtained 259 images of Ceres using the High Resolution Channel of the Advanced Camera for Surveys on the Hubble Space Telescope. These images were obtained at high temporal sampling in three filter bands (V, U, and Mid-UV) over the entire rotational phase of Ceres. The resolution was 30 km/pixel, allowing us to detect and follow the motions of surface features on Ceres for the first time. Light and dark patches are seen on the surface, with high contrast and differences among the three filters. A strong feature near the equator provided a control point to definitively determine the rotational pole of Ceres: RA=291 deg and Dec=59 deg. Based on limb fits to an accuracy of nearly 0.1 pixel, our shape measurements show that Ceres is rotationally symmetric with an equatorial radius of 487.3 km and a polar radius of 454.7 km with roughly 5 km uncertainties. This flattening is significantly less than expected for a relaxed body of Ceres' mean density and rotation period, but it is consistent with such a body if Ceres has a central rocky core surrounded by water ice. Support for this project is through STScI grant HST-GO-09748.
DE: 6035 Orbital and rotational dynamics
DE: 6055 Surfaces and interiors
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting