title: The Cassini UVIS stellar probe of the Titan atmosphere.
abstract: The Cassini Ultraviolet Imaging Spectrometer (UVIS) observed the extinction of photons from two stars by the atmosphere of Titan during the Titan flyby. Six species were identified and measured: methane, acetylene, ethylene, ethane, diacetylene, and hydrogen cyanide. The observations cover altitudes from 450 to 1600 kilometers above the surface. A mesopause is inferred from extraction of the temperature structure of methane, located at 615 km with a temperature minimum of 114 kelvin. The asymptotic kinetic temperature at the top of the atmosphere determined from this experiment is 151 kelvin. The higher order hydrocarbons and hydrogen cyanide peak sharply in abundance and are undetectable below altitudes ranging from 750 to 600 km, leaving methane as the only identifiable carbonaceous molecule in this experiment below 600 km.
authors.affiliation: Department of Aerospace Engineering, University of Southern California, University Park, Los Angeles, CA 90089, USA. dons@hippolyta.usc.edu
authors.forename: Donald E
authors.initials: DE
authors.lastname: Shemansky
authors.forename: A Ian F
authors.initials: AI
authors.lastname: Stewart
authors.forename: Robert A
authors.initials: RA
authors.lastname: West
authors.forename: Larry W
authors.initials: LW
authors.lastname: Esposito
authors.forename: Janet T
authors.initials: JT
authors.lastname: Hallett
authors.forename: Xianming
authors.initials: X
authors.lastname: Liu
mesh_terms: D000114:Acetylene; D001272:Atmosphere; D004980:Ethane; D005030:Ethylenes; D005118:Extraterrestrial Environment; D006839:Hydrocarbons, Acyclic; D006856:Hydrogen Cyanide; D008433:Mathematics; D008697:Methane; D018539:Saturn; D018531:Spacecraft; D013057:Spectrum Analysis; D013696:Temperature
chemical_list: D005030:Ethylenes; D006839:Hydrocarbons, Acyclic; D006856:Hydrogen Cyanide; C036216:ethylene; D004980:Ethane; D000114:Acetylene; D008697:Methane