Ultraviolet emission from CG's coma: fluorescence versus electron-impact excitation

Wednesday, 16 December 2015: 15:10
3014 (Moscone West)
Eric Schindhelm1, Michael F A'Hearn2, Lori M Feaga2, Paul D Feldman3, Kathleen Mandt4, Joel W Parker1, Andrew Steffl5, Alan Stern6 and Harold A Weaver Jr7, (1)Southwest Research Institute Boulder, Boulder, CO, United States, (2)University of Maryland, College Park, MD, United States, (3)Johns Hopkins University, Baltimore, MD, United States, (4)Southwest Research Institute, San Antonio, TX, United States, (5)Southwest Research Institute Boulder, Dept Space Studies, Boulder, CO, United States, (6)Southwest Research Institute, Boulder, CO, United States, (7)Johns Hopkins Applied Physics Laboratory, Laurel, MD, United States
Alice is a lightweight, low-power far-ultraviolet (750 - 2000 Angstroms) spectrograph onboard Rosetta designed for in situ imaging spectroscopy of a cometary coma during the rendezvous with comet 67P/Churyumov-Gerasimenko. After arrival at CG, Alice observed emission resulting from electron-impact dissociation of parent molecules in the coma. Such emission, combined with in-situ measurements of the electron environment from the Rosetta Plasma Consortium instruments, reveals the composition and time-variability of species in the coma. We compare lines of sight to the shadowed nucleus to different views through the coma to distinguish between electron impact excited emission and fluorescent emission from photo-dissociation daughter products. We will present analysis of these processes for data from the beginning of escort through perihelion.