P41E-08
Radii and Shape of Pluto and Charon: Preliminary Results from New Horizons

Thursday, 17 December 2015: 09:30
2022-2024 (Moscone West)
Francis Nimmo1, Carey Michael Lisse2, Orkan M Umurhan3, William B McKinnon4, Marc W Buie5, Tod Lauer6, Ross A Beyer7, Jeffrey M Moore7, Alan Stern8, Harold A Weaver Jr2, Catherine Olkin5, Kimberly Ennico Smith7, Leslie Ann Young5, Carver Jay Bierson9 and The New Horizons Geology Geophysics and Imaging Team, (1)University of California-Santa Cruz, Department of Earth and Planetary Sciences, Santa Cruz, CA, United States, (2)Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States, (3)SETI Institute Mountain View, Mountain View, CA, United States, (4)Washington University in St Louis, St. Louis, MO, United States, (5)Southwest Research Institute Boulder, Boulder, CO, United States, (6)National Optical Astronomy Observatory, Tucson, AZ, United States, (7)NASA Ames Research Center, Moffett Field, CA, United States, (8)Southwest Research Institute, Boulder, CO, United States, (9)University of California Santa Cruz, Santa Cruz, CA, United States
Abstract:
Accurate determinations of the mean radii of Pluto and Charon are important for establishing their densities and thus bulk composition. A fossil bulge, if present, would place constraints on the thermal and orbital evolution of these bodies [1,2]. The New Horizons LORRI imaging system [3] has provided global images of Pluto and Charon, with best resolutions of 3.8 and 2.3 km/pix, respectively. Three separate approaches have been used to determine mean radii and shape from the images, two using a threshold DN value [4,5] and one using a maximum gradient method. These approaches were validated using synthetic images having a range of photometric functions. Tradeoffs between the limb center location and the derived shape in individual images can be reduced by combining limb picks from different images. Preliminary results for both Pluto and Charon will be presented.

[1] Robuchon & Nimmo, Icarus 216, 426, 2011. [2] McKinnon & Singer, DPS 46, abs. no. 419.07, 2014. [3] Cheng et al., SSR 140, 189, 2008. [4] Dermott & Thomas, Icarus 73, 25, 1988. [5] Thomason & Nimmo, LPSC 46, abs. no. 1462, 2015.

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