Titan occultations of Orion's belt observed with Cassini/UVIS

Abstract On 1 February 2016 Titan occulted the three stars in Orion’s belt, as seen from the Casssini spacecraft. The ultraviolet spectrometer on Cassini observed this event with the stars arranged along the instrument’s entrance slit. These three stellar occultations probed different latitudes in Titan’s northern hemisphere but similar longitudes. The occultations were also observed simultaneously in the extreme ultraviolet and far ultraviolet regions of the spectrum. Analysis of these measurements provides information on the atmospheric composition and thermal structure. We determine altitude profiles of N 2 , CH 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 , C 4 H 2 , C 6 H 6 , HCN, and HC 3 N densities along with aerosol extinction. We infer significant variations in latitude for C 2 H 2 , C 2 H 4 , C 4 H 2 , aerosols, and temperature, providing clues to global circulations patterns. The inferred mole fractions of C 2 H 2 , C 2 H 4 , C 4 H 2 , C 6 H 6 , HCN, and HC 3 N are roughly consistent with photochemical model predictions, but C 2 H 2 and C 2 H 4 are over predicted by tens of percent at pressures greater than 10−5 hPa, C 4 H 2 is under predicted by ∼ x2 at most levels, and C 6 H 6 is under predicted by ∼ x2 at pressures less than 10−5 hPa.