Observations of Comet ISON (C/2012 S1) from Lowell Observatory

Manuscript: 25 pages text (single spaced), 5 tables, 6 figures We observed dynamically new sungrazing comet ISON (C/2012 S1) exten-sively at Lowell Observatory throughout 2013 in order to characterize its behav-ior prior to perihelion. ISON had “typical ” abundances for an Oort Cloud comet. Its dust production, as measured by Afρ, remained nearly constant during the apparition but its CN gas production increased by ∼50×. The minimum active area necessary to support observed water production rates exceeded the likely surface area of the nucleus and suggests a population of icy grains in the coma. Together with the flattening of the dust radial profile over time, this is consistent with ejection of a large quantity of slow moving dust and icy grains in the coma at large heliocentric distance. The dust morphology was dominated by the tail