Titan airglow spectra from the Cassini Ultraviolet Imaging Spectrograph: FUV disk analysis

[en] We present a spectral analysis of the far ultraviolet (FUV: 1150–1900 A ° ) disk airglow observations of Titan’s atmosphere by the Cassini Ultraviolet Imaging Spectrograph (UVIS). The FUV spectrum consists of emissions from the Lyman-Birge-Hopfield (LBH) band system of N2 excited by photoelectrons (a 1Pg ! X 1Sg+), N I multiplets from solar photodissociative excitation of N2, resonantly scattered solar H Ly-a and sunlight reflected by N2 in the mesosphere-stratosphere and modified by aerosols (e.g.,tholins) and hydrocarbon absorption. Below 1450 A, the strongest emissions arise from H Ly-a with an intensity of 208 Rayleighs (R), LBH bands with an intensity of 43 R, and the N I multiplets with a combined intensity of 16 R. Above 1450 A , most of the UVIS signal is due to reflected sunlight. Mixing ratios of tholins, C2H2, C2H4 and C4H2 have been derived from the reflected sunlight using a Rayleigh scattering model. The derived mixing ratios are in good agreement with Voyager infrared observations and with FUV photochemical models, assuming solar energy deposition above 1450 A occurs near 250 km (Wilson and Atreya, 2004). We also present the first geometric albedo measurement of Titan from 1500–1900 A

Disciplines :

Space science, astronomy & astrophysics

Author, co-author :

Ajello, Joseph M.

Gustin, Jacques ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Physique des atmosphères et des environnements planétaires

Stewart, Ian

Larsen, Kristopher

Esposito, Larry

Pryor, Wayne

McClintock, William

Stevens, Michael

Malone, Charles

Dziczek, Darius

Language :

English

Title :

Titan airglow spectra from the Cassini Ultraviolet Imaging Spectrograph: FUV disk analysis

Publication date :

2008

Journal title :

Geophysical Research Letters

ISSN :

0094-8276

eISSN :

1944-8007

Publisher :

American Geophysical Union, Washington, United States - District of Columbia

Peer reviewed :

Peer Reviewed verified by ORBi

Available on ORBi :

since 06 August 2012

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Bibliography

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