Far-Ultraviolet Surface Reflectance of Comet 67P/Churyumov-Gerasimenko as Observed by the Alice Spectrograph on Rosetta

Wednesday, 17 December 2014: 1:55 PM
Lori M Feaga1, S Alan Stern2, Michael F A'Hearn1, Jean-Loup Bertaux3, Paul D Feldman4, Joel Wm Parker2, Eric Schindhelm2, Andrew J Steffl2, Harold A Weaver Jr5 and Silvia Protopapa1, (1)University of Maryland, College Park, MD, United States, (2)Southwest Research Institute Boulder, Dept Space Studies, Boulder, CO, United States, (3)University of Versailles Saint-Quentin en Yvelines, Versailles, France, (4)Johns Hopkins University, Baltimore, MD, United States, (5)Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States
Alice, NASA’s light weight and low power far-ultraviolet (FUV) imaging spectrograph onboard ESA’s comet rendezvous mission Rosetta (Stern et al. 2007), is in the process of characterizing the nucleus, coma, and nucleus/coma coupling of its primary target comet 67P/Churyumov-Gerasimenko (C-G), a Jupiter Family comet with perihelion distance of 1.29 AU and a distinct bi-lobed shape. With a spectral range from 750-2000 Å and spatial resolution of 30 m by 150 m at the comet from a spacecraft distance of 30 km, Alice will map the surface of C-G obtaining the first far-ultraviolet (FUV) spectral data set of a spatially resolved comet nucleus, studying the chemical heterogeneity of the nucleus, and determining albedo and color variation between the two lobes. Following successful instrument re-commissioning in March 2014, Alice began studying the surface at the end of July as Rosetta approached its target and determined, as expected from the UV behavior of many refractory materials, that C-G has a low FUV albedo. Subsequent observations made during the pre-landing and landing phases of the mission will be presented and discussed in the context of contemporaneous in situ and other remote sensing measurements, including FUV spectra of C-G highlighting spectral features of the landing site region.