29 juin-1 juil. 2022 Lyon (France)
Updated radiative transfer model for Titan in the near-infrared wavelength range: Validation on Huygens atmospheric and surface measurements and application to the analysis of the VIMS/Cassini observations of the Dragonfly landing area
Maël Es-Sayeh  1@  , Sébastien Rodriguez, Maélie Coutelier  2  , Pascal Rannou  3@  , Bruno Bézard  4@  , Luca Maltagliati  5  , Thomas Cornet  6@  , Bjorn Grieger  7@  , Erich Karkoschka  8@  , Benoit Seignovert  9@  , Stéphane Le Mouélic  10@  , Christophe Sotin  11@  , Athena Coustenis  12@  
1 : ES-SAYEH
Institut de Physique du Globe de Paris, Université Paris Cité
2 : LATMOS
INSU, Université de Nantes
3 : Groupe de spectrométrie moléculaire et atmosphérique - UMR 7331
Université de Reims Champagne-Ardenne : UMR7331, Centre National de la Recherche Scientifique : UMR7331
4 : Laboratoire d'études spatiales et d'instrumentation en astrophysique  (LESIA)  -  Site web
Université Pierre et Marie Curie [UPMC] - Paris VI, Observatoire de Paris, INSU, CNRS : UMR8109, Université Paris VII - Paris Diderot, Université Pierre et Marie Curie (UPMC) - Paris VI
5, place Jules Janssen 92190 MEUDON -  France
5 : Nature Astronomy Springer Nature Research
6 : European Space Agency, European Space Astronomy Centre  (ESA)
P.O. BOX 78, Villanueva de la Cañada (Madrid) -  Espagne
7 : Aurora for ESA, Villanueva de la Canada
8 : Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721-0092, USA
9 : Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement  (LGL-TPE)  -  Site web
CNRS : UMR5276, INSU, Université Claude Bernard - Lyon I, École Normale Supérieure (ENS) - Lyon
Université Claude Bernard Lyon 1. UMR CNRS 5276 LGLTPE Bâtiment Géode 2, rue R. Dubois 69100 Villeurbanne -  France
10 : Laboratoire de Planétologie et Géodynamique de Nantes  (LPGN)
CNRS : UMR6112, INSU, Université de Nantes
2 Rue de la Houssinière - BP 92208 44322 NANTES CEDEX 3 -  France
11 : Laboratoire de Planétologie et Géodynamique de Nantes
UMR6112
12 : Laboratoire d'études spatiales et d'instrumentation en astrophysique  (LESIA)  -  Site web
Université Pierre et Marie Curie (UPMC) - Paris VI, Observatoire de Paris, CNRS : UMR8109, Université Paris VII - Paris Diderot
5, place Jules Janssen 92190 MEUDON -  France

Titan is the only moon in the solar system with a thick atmosphere, dominated with nitrogen and organic compounds and a methane- and ethane-based climatic cycles similar to the hydrological cycle on Earth. Hence, Titan is a prime target for planetary and astrobiological researches. Heaviest organic materials resulting from atmospheric chemistry (including high atomic number aerosols) precipitate onto the surface and are subject to geological processes (e.g., eolian and fluvial erosion) that lead to the formation of a variety of landscapes, including dune fields, river networks, mountains, canyons, lakes and seas, analogous to their terrestrial counterparts. The analysis of the surface reflectivity in the near-infrared (NIR) allows to constrain the surface composition, which in turn is crucial to understand the processes leading to the formation and evolution of planetary landscapes. However, Titan's atmosphere prevents the surface from being probed in the NIR. Incident and reflected solar radiations are strongly affected by gaseous absorption and aerosol scattering at almost all the wavelengths in the NIR. Only where the methane absorption weak enough, narrow transmission windows allow the detection of radiation coming from the low atmosphere and from the surface. In the 0.88-5.11 μm range, the Visual and Infrared Mapping Spectrometer (VIMS) instrument on board the Cassini spacecraft has shown that the surface can be observed in eight transmission windows centered at 0.93, 1.08, 1.27, 1.59, 2.03, 2.69, and 2.78 μm, and in the 5.0-5.11 μm interval. We present an analysis of Titan data acquired by VIMS, making use of an updated radiative transfer model with up-to-date gaseous abundances profiles and absorption coefficients and improved photochemical aerosol optical properties. Our RT model is validated using the in situ observations of DISR acquired during descent and once landed. We apply our model to four hyper-spectral VIMS cubes over the Selk crater which is the Dragonfly Landing Area, drastically diminishing seams between cubes due to atmosphere and varying observation geometry. Coupled with an efficient inversion scheme, our model can be apply to the Cassini's VIMS complete dataset for the retrieval of Titan's atmospheric opacity and surface albedos at regional and global scales.


Personnes connectées : 7 Vie privée
Chargement...