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6 results on '"M. Hirtzig"'

1. The Spectral Nature of Titan's Major Geomorphological Units: Constraints on Surface Composition

Author

Bernard Schmitt, S. D. Wall, S. Philippe, Emmanuel Bratsolis, Christophe Sotin, S. Le Mouélic, Olivier Witasse, A. Solomonidou, Katrin Stephan, Rosaly M. C. Lopes, Charles Elachi, A. Le Gall, Jani Radebaugh, E. Villanueva, A. Anthony Bloom, M. Hirtzig, Robert H. Brown, Athena Coustenis, Kenneth J. Lawrence, Christos Matsoukas, Nicolas Altobelli, M. A. Janssen, Michael Malaska, Pierre Drossart, Sebastien Rodriguez, Jérémy F. Brossier, Ashley Schoenfeld, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), European Space Astronomy Centre (ESAC), European Space Agency (ESA), Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Fondation La main à la pâte, Department of Physics [Athens], National and Kapodistrian University of Athens = University of Athens (NKUA | UoA), Department of Geological Sciences [BYU], Brigham Young University (BYU), DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Laboratoire de Planétologie et Géodynamique UMR6112 (LPG), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA), IMPEC - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), Royal Institute of Technology [Stockholm] (KTH ), Department of Earth, Planetary and Space Sciences [Los Angeles] (EPSS), University of California [Los Angeles] (UCLA), University of California-University of California, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Agence Spatiale Européenne = European Space Agency (ESA), NASA-California Institute of Technology (CALTECH), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), National and Kapodistrian University of Athens (NKUA), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), PLANETO - LATMOS, Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), University of California (UC)-University of California (UC), and Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
Synthetic aperture radar, Haze, 010504 meteorology & atmospheric sciences, Spectral response, Atmospheric sciences, Titan geology, 01 natural sciences, Latitude, symbols.namesake, Geochemistry and Petrology, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), Radiative transfer, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, [PHYS]Physics [physics], saturnian satellites, Geophysics, 13. Climate action, Space and Planetary Science, radiative transfer, [SDU]Sciences of the Universe [physics], symbols, Evolution theories, Water ice, spectral behavior, geomorphological units, Titan composition, Titan (rocket family), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Geology
Abstract

We investigate Titan's low‐latitude and midlatitude surface using spectro‐imaging near‐infrared data from Cassini/Visual and Infrared Mapping Spectrometer. We use a radiative transfer code to first evaluate atmospheric contributions and then extract the haze and the surface albedo values of major geomorphological units identified in Cassini Synthetic Aperture Radar data, which exhibit quite similar spectral response to the Visual and Infrared Mapping Spectrometer data. We have identified three main categories of albedo values and spectral shapes, indicating significant differences in the composition among the various areas. We compare with linear mixtures of three components (water ice, tholin‐like, and a dark material) at different grain sizes. Due to the limited spectral information available, we use a simplified model, with which we find that each albedo category of regions of interest can be approximately fitted with simulations composed essentially by one of the three surface candidates. Our fits of the data are overall successful, except in some cases at 0.94, 2.03, and 2.79 μm, indicative of the limitations of our simplistic compositional model and the need for additional components to reproduce Titan's complex surface. Our results show a latitudinal dependence of Titan's surface composition, with water ice being the major constituent at latitudes beyond 30°N and 30°S, while Titan's equatorial region appears to be dominated partly by a tholin‐like or by a very dark unknown material. The albedo differences and similarities among the various geomorphological units give insights on the geological processes affecting Titan's surface and, by implication, its interior. We discuss our results in terms of origin and evolution theories.

Published
2018
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2. TandEM: Titan and Enceladus mission

Author

J. E. Blamont, Tobias Owen, Michael Küppers, Xenophon Moussas, Robert H. Brown, Nicole Schmitz, Sascha Kempf, C. Menor Salvan, T. W. Haltigin, Olivier Grasset, Roger V. Yelle, Wayne H. Pollard, Daniel Gautier, Paul R. Mahaffy, Joe Pitman, Iannis Dandouras, Daphne Stam, John C. Zarnecki, Bruno Sicardy, Georges Durry, Jesús Martínez-Frías, Norbert Krupp, S. Le Mouélic, Matthias Grott, Sébastien Lebonnois, T. Krimigis, Elizabeth P. Turtle, Alain Herique, Linda Spilker, Ralph D. Lorenz, Maria Teresa Capria, M. Combes, John F. Cooper, O. Mousis, Joachim Saur, Wlodek Kofman, J. Bouman, M. Paetzold, Hojatollah Vali, C. Dunford, Sushil K. Atreya, Eric Chassefière, I. de Pater, T. B. McCord, Bruno Bézard, Gabriel Tobie, Catherine D. Neish, M. Ruiz Bermejo, Sergei Pogrebenko, Kim Reh, Athena Coustenis, Ralf Jaumann, Angioletta Coradini, Leonid I. Gurvits, Andrew J. Coates, Tibor S. Balint, H. Hussmann, E. Choi, Ioannis A. Daglis, Edward C. Sittler, Emmanuel Lellouch, Robert A. West, L. Boireau, E.F. Young, Timothy A. Livengood, Cesar Bertucci, Martin G. Tomasko, M. Fujimoto, Ingo Müller-Wodarg, Yves Bénilan, Wing-Huen Ip, Marina Galand, Darrell F. Strobel, Cyril Szopa, Pascal Rannou, D. G. Mitchell, Mark Leese, Véronique Vuitton, P. Annan, Tetsuya Tokano, Caitlin A. Griffith, Conor A. Nixon, Stephen A. Ledvina, Karoly Szego, Andrew Morse, Panayotis Lavvas, Luisa Lara, C. de Bergh, Jonathan I. Lunine, R. A. Gowen, Katrin Stephan, Jianping Li, Glenn S. Orton, Michel Blanc, Esa Kallio, Ronan Modolo, M. Hirtzig, Helmut Lammer, Nicholas Achilleos, D. Nna Mvondo, Frank Sohl, M. Nakamura, Andrew Steele, C. C. Porco, Marcello Fulchignoni, Gordon L. Bjoraker, Olga Prieto-Ballesteros, J. J. López-Moreno, Andrew Dominic Fortes, Rafael Rodrigo, Patrice Coll, Francesca Ferri, François Raulin, Tom Spilker, F. J. Crary, J. H. Waite, Dirk Schulze-Makuch, Thomas E. Cravens, Kevin H. Baines, C. P. McKay, L. Richter, D. Luz, David H. Atkinson, Martin Knapmeyer, Robert E. Johnson, D. Fairbrother, F. M. Flasar, Roland Thissen, Paul N. Romani, Sebastien Rodriguez, Urs Mall, Paul M. Schenk, Franck Hersant, R. Koop, Odile Dutuit, I. Vardavas, T. Kostiuk, Ricardo Amils, Konrad Schwingenschuh, Robert V. Frampton, Fritz M. Neubauer, Jan-Erik Wahlund, L. A. Soderblom, Michele K. Dougherty, Anna Milillo, Frank T. Robb, Bernard Schmitt, Christophe Sotin, Michel Cabane, A. Selig, Bernard Marty, Yves Langevin, Rosaly M. C. Lopes, Emmanuel T. Sarris, E. De Angelis, D. Toublanc, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor] (AOSS), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Space and Atmospheric Physics Group [London], Blackett Laboratory, Imperial College London-Imperial College London, Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' (CISAS), Università degli Studi di Padova = University of Padua (Unipd), Mullard Space Science Laboratory (MSSL), University College of London [London] (UCL), Joint Institute for VLBI in Europe (JIVE ERIC), Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), The Open University [Milton Keynes] (OU), NASA Ames Research Center (ARC), Department of Physics [Athens], National and Kapodistrian University of Athens (NKUA), University of Cologne, Institute for Astronomy [Honolulu], University of Hawai‘i [Mānoa] (UHM), Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA (UMR_7583)), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), NASA Goddard Space Flight Center (GSFC), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Swedish Institute of Space Physics [Uppsala] (IRF), Space Science Division [San Antonio], Southwest Research Institute [San Antonio] (SwRI), Centre National d'Études Spatiales [Toulouse] (CNES), Centre d'étude spatiale des rayonnements (CESR), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Academy of Athens, Observatoire de Paris - Site de Paris (OP), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Space Science Institute [Boulder] (SSI), Bombardier Aerospace, Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Sensors and Software, University of Idaho [Moscow, USA], SRON Netherlands Institute for Space Research (SRON), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Istituto Nazionale di Astrofisica (INAF), University of Kansas [Lawrence] (KU), National Observatory of Athens (NOA), Department of Astronomy [Berkeley], University of California [Berkeley] (UC Berkeley), University of California (UC)-University of California (UC), Service d'aéronomie (SA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie de Grenoble (LPG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency [Sagamihara] (JAXA), McGill University = Université McGill [Montréal, Canada], FORMATION STELLAIRE 2009, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB), Institute of Astronomy [Taiwan] (IANCU), National Central University [Taiwan] (NCU), University of Virginia [Charlottesville], Finnish Meteorological Institute (FMI), Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Gesellschaft, DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics [Beijing] (IAP), Chinese Academy of Sciences [Beijing] (CAS)-Chinese Academy of Sciences [Beijing] (CAS), National Center for Earth and Space Science Education (NCESSE), Observatório Astronómico de Lisboa, Centre de Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Bear Fight Center, Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) (UTINAM), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Lockheed Martin Space, Groupe de spectrométrie moléculaire et atmosphérique (GSMA), Université de Reims Champagne-Ardenne (URCA)-Centre National de la Recherche Scientifique (CNRS), University of Maryland Biotechnology Institute Baltimore, University of Maryland [Baltimore], Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Democritus University of Thrace (DUTH), Lunar and Planetary Institute [Houston] (LPI), School of Earth and Environmental Sciences [Pullman], Washington State University (WSU), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universita degli Studi di Padova, National and Kapodistrian University of Athens = University of Athens (NKUA | UoA), Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique UMR6112 (LPG), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Spain] (CSIC), IMPEC - LATMOS, University of California [Berkeley], University of California-University of California, Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), McGill University, École normale supérieure - Paris (ENS Paris)-École normale supérieure - Paris (ENS Paris), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Université de Franche-Comté (UFC)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), University of Virginia, Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)

Subjects
Exploration of Saturn, Solar System, Cosmic Vision, 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Computer science, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], TandEM, 01 natural sciences, law.invention, Astrobiology, Enceladus, Orbiter, symbols.namesake, law, Saturnian system, 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Spacecraft, Tandem, business.industry, Astronomy and Astrophysics, Landing probes, Space and Planetary Science, symbols, Titan, business, Titan (rocket family)
Abstract

著者人数：156名, Accepted: 2008-05-27, 資料番号: SA1000998000

Published
2009
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3. An empirical line list for methane in the 1.26-1.71 μm region for planetary investigations (T = 80-300 K). Application to Titan

Author

E. Lellouch, Pierre Drossart, Catherine de Bergh, Bruno Bézard, L. Wang, Didier Mondelain, Athena Coustenis, Alain Campargue, M. Hirtzig, Samir Kassi, LAME, Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères] (LIPhy), Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), LAsers, Molécules et Environnement (LAME-LIPhy), Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), and Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, [PHYS]Physics [physics], 010304 chemical physics, Differential optical absorption spectroscopy, Near-infrared spectroscopy, Astronomy and Astrophysics, Natural abundance, 01 natural sciences, 7. Clean energy, Methane, Spectral line, Computational physics, symbols.namesake, chemistry.chemical_compound, chemistry, 13. Climate action, Space and Planetary Science, 0103 physical sciences, symbols, Atmosphere of Titan, Spectroscopy, Titan (rocket family), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Remote sensing
Abstract

Insufficient knowledge of the near infrared spectrum of methane is an important limitation for the analysis of the spectra of Titan and of the outer planetary atmospheres in general. The work reported here is the result of a long-term project aiming to provide astronomers with a line by line list for precise calculations of the methane absorption in the near infrared region. We thus present here our best to date empirical line list between 5854 and 7919 cm−1 (1.71–1.26 μm) and apply it to Titan, demonstrating its capability to significantly improve planetary spectral analysis. In recent contributions, we have obtained empirical line lists at room temperature and at 80 K (suitable for Titan conditions) from spectra recorded by (i) Differential Absorption Spectroscopy (DAS) in the high energy part of the tetradecad (5854–6195 cm−1) and in the icosad (6717–7589 cm−1) (ii) high sensitivity CW-Cavity Ring Down Spectroscopy (CRDS) in the 1.58 μm and 1.28 μm transparency windows (6165–6750 cm−1 and 7541–7919 cm−1, respectively). In this work, we construct the global line lists for methane in “natural” isotopic abundance, covering the entire spectral region from 5854 to 7919 cm−1. These WKMC (for Wang, Kassi, Mondelain, Campargue) empirical lists include 42,988 and 46,320 lines at 80 ± 3 K and 296 ± 3 K, respectively and are assembled here with some important improvements: (i) New spectroscopic parameters for the 5854–6148 cm−1 region at 80 K which increase significantly the number of observations and lower state energy determinations. (ii) Transitions of 13CH4 and CH3D were systematically identified by comparison with DAS spectra of highly enriched 13CH4 and CH3D, recorded at the same temperatures. (iii) In the 1.58 μm transparency window where CH3D lines contribute importantly to the methane spectrum at 80 K, the set of CH3D lower state energy values was completed by using recent DAS results for pure CH3D. The “two temperature method” provided lower state energy values for about 24,000 transitions from the ratios of their line intensities at 80 K and 296 K. The clear propensity of the derived low J values of 12CH4 and 13CH4 to be integer illustrates the quality of the lower state energy values. The obtained data sets allow us to account for most of the temperature dependence of the absorption over the considered region. To illustrate the interest of the WKMC line lists for planetary applications, we perform simulations of Titan spectra at different resolutions taken from the ground with instruments such as the FTS at the CFHT and CRIRES at the VLT or by the DISR instrument on board the Huygens probe. The agreement between the simulations and the observations clearly demonstrates an important improvement with respect to previous works.

Published
2012
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4. Applications of a new set of methane line parameters to the modeling of Titan's spectrum in the 1.58 μm window

Author

E. Lellouch, M. Hirtzig, Samir Kassi, L. Wang, Vincent Boudon, Andrei Nikitin, Pierre Drossart, Bruno Bézard, Catherine de Bergh, Pascal Rannou, Vladimir G. Tyuterev, Régis Courtin, Athena Coustenis, Alain Campargue, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Groupe de spectrométrie moléculaire et atmosphérique (GSMA), Université de Reims Champagne-Ardenne (URCA)-Centre National de la Recherche Scientifique (CNRS), LAsers, Molécules et Environnement (LAME-LIPhy), Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères] (LIPhy), Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Laboratoire Interdisciplinaire Carnot de Bourgogne (LICB), Université de Bourgogne (UB)-Centre National de la Recherche Scientifique (CNRS), Laboratory of Theoretical Spectroscopy [Tomsk] (LTS), V.E. Zuev Institute of Atmospheric Optics (IAO), Siberian Branch of the Russian Academy of Sciences (SB RAS)-Siberian Branch of the Russian Academy of Sciences (SB RAS), Laboratoire d'études spatiales et d'instrumentation en astrophysique ( LESIA ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire de Météorologie Dynamique (UMR 8539) ( LMD ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -École polytechnique ( X ) -École des Ponts ParisTech ( ENPC ) -Centre National de la Recherche Scientifique ( CNRS ) -Département des Géosciences - ENS Paris, École normale supérieure - Paris ( ENS Paris ) -École normale supérieure - Paris ( ENS Paris ), Groupe de spectrométrie moléculaire et atmosphérique - UMR 7331 ( GSMA ), Université de Reims Champagne-Ardenne ( URCA ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire de Spectrométrie Physique ( LSP ), Université Joseph Fourier - Grenoble 1 ( UJF ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Interdisciplinaire Carnot de Bourgogne ( LICB ), Université de Bourgogne ( UB ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratory of Theoretical Spectroscopy [Tomsk] ( LTS ), V.E. Zuev Institute of Atmospheric Optics ( IAO ), Siberian Branch of the Russian Academy of Sciences ( SB RAS ) -Siberian Branch of the Russian Academy of Sciences ( SB RAS ), LIPhy-LAME, Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères] ( LIPhy ), Université Joseph Fourier - Grenoble 1 ( UJF ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Joseph Fourier - Grenoble 1 ( UJF ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Laboratoire de Spectrométrie Physique (LSP), Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), and Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB)

Subjects
010504 meteorology & atmospheric sciences, Infrared, CASSINI VIMS, HUYGENS PROBE, MONODEUTERATED METHANE, Atmospheric sciences, 01 natural sciences, 7. Clean energy, Methane, Spectral line, Troposphere, chemistry.chemical_compound, symbols.namesake, 0103 physical sciences, Spectral resolution, Spectroscopy, 010303 astronomy & astrophysics, CLOUD STRUCTURE, 0105 earth and related environmental sciences, Physics, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], [ PHYS.PHYS.PHYS-OPTICS ] Physics [physics]/Physics [physics]/Optics [physics.optics], Astronomy and Astrophysics, 9500 CM(-1), SPECTROSCOPIC DATABASE, M TRANSPARENCY WINDOW, Computational physics, Aerosol, chemistry, [ PHYS.PHYS.PHYS-AO-PH ] Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], TEMPERATURE-DEPENDENCE, 13. Climate action, Space and Planetary Science, symbols, SHIFT COEFFICIENTS, OUTER SOLAR-SYSTEM, Titan (rocket family)
Abstract

International audience; In this paper we apply a recently released set of methane line parameters (Wang et al., 2011) to the modeling of Titan spectra in the 1.58 mu m window at both low and high spectral resolution. We first compare the methane absorption based on this new set of methane data to that calculated from the methane absorption coefficients derived in situ from DISR/Huygens (Tomasko et al., 2008a; Karkoschka and Tomasko, 2010) and from the band models of Irwin et al. (2006) and Karkoschka and Tomasko (2010). The Irwin et al. (2006) band model clearly underestimates the absorption in the window at temperature-pressure conditions representative of Titan's troposphere, while the Karkoschka and Tomasko (2010) band model gives an acceptable agreement in the whole window, overestimating the absorption by about 15% in the range 6300-6500 cm(-1). We also find that the transmittance of Titan's atmosphere is in excellent agreement with that calculated from the Tomasko et al. (2008a) coefficients after reducing them by about 7%. Synthetic spectra computed with spectral resolutions of 1.2 cm(-1) (R similar to 5400) and 0.35 cm(-1) (R similar to 18000) are then compared with two high-resolution Earth-based measurements of Titan's albedo obtained in 1982 and 1993 (with KPNO/FTS and IRTF/CSHELL). The new set of methane line parameters leads to an excellent match of all the CH3D and CH4 absorption features in these spectra, and permits us to derive a ratio of CH3D/CH4=(4.5 +/- 1.0) x 10(-4) - hence a D/H ratio in methane for Titan of (1.13 +/- 0.25) x 10(-4) - and a CO mole fraction of 40 +/- 10 ppm (from the KPNO/FTS dataset) and 51 +/- 7 ppm (from the IRTF/CSHELL dataset). We also infer constraints on the far-wing lineshape of methane lines of the 2v(3) band. We finally present two other examples of models of Titan's spectrum using the new line parameters, one potentially useful for future higher-resolution (R=40,000) observations, another one applicable to the ongoing low-resolution (R similar to 100) observations by Cassini VIMS. We show that the aerosol model of Tomasko et al. (2008b) produces too much intensity at low phase angle compared to a VIMS spectrum recorded near the Huygens site and we propose a slightly revised model that reproduces this observation.

Published
2012
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5. The 2-μm spectroscopy of Huygens probe landing site on Titan with Very Large Telescope/Nasmyth Adaptive Optics System Near-Infrared Imager and Spectrograph

Author

A. Coustenis, M. Combes, A. Negrão, M. Hirtzig, Vincent Boudon, Pierre Drossart, Pascal Rannou, Eric Gendron, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Observatório Astronómico de Lisboa, Service d'aéronomie (SA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique de l'Université de Bourgogne (LPUB), Université de Bourgogne (UB)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Laboratoire de Planétologie et Géodynamique UMR6112 (LPG), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - Faculté des Sciences et des Techniques, and Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA)

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, Soil Science, Aquatic Science, Oceanography, 01 natural sciences, Spectral line, adaptive optics, symbols.namesake, Optics, Geochemistry and Petrology, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), Radiative transfer, surface, Spectroscopy, Adaptive optics, 010303 astronomy & astrophysics, Spectrograph, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Physics, Very Large Telescope, Ecology, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], business.industry, Near-infrared spectroscopy, Paleontology, Forestry, haze, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Geophysics, 13. Climate action, Space and Planetary Science, radiative transfer, Huygens, symbols, business, Titan (rocket family), Titan
Abstract

[1] Several ground-based telescopes followed the event of the Huygens probe descent through Titan's atmosphere (14 January 2005). We used the Nasmyth Adaptive Optics System Near-Infrared Imager and Spectrograph (NACO) adaptive optics system at the UT-4 of the Very Large Telescope in Chile to perform both spectroscopic and imaging measurements of Titan. We present here a selected sample of the spectra we acquired on 16 January 2005 in the K band between 2.03 and 2.40 μm. Our spectra include the Huygens landing site and surrounding dark and bright areas. We apply a radiative transfer code using new methane absorption coefficients calculated in the 2-μm region. The analysis of the data yields information on the atmosphere and surface properties of these areas. The latter seem to indicate a strong decrease of Titan's surface albedo between 2.03 and 2.12 μm in all areas. This is compatible with the presence of ices such as CH4 and H2O at the surface. Sensitivity tests on the influence of the haze profile and the methane absorption on these results were performed.

Published
2007
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6. Near-infrared study of Titan's resolved disk in spectro-imaging with CFHT/OASIS

Author

M. Hirtzig, A. Pecontal-Rousset, A. Negrao, E. Emsellem, Olivier Lai, Pascal Rannou, Bernard Schmitt, Athena Coustenis, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Service d'aéronomie (SA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie de Grenoble (LPG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, 010504 meteorology & atmospheric sciences, biology, Astronomy, Flux, Astronomy and Astrophysics, Albedo, biology.organism_classification, 01 natural sciences, Atmosphere, symbols.namesake, 13. Climate action, Space and Planetary Science, Geometric albedo, 0103 physical sciences, symbols, Radiative transfer, Spectral resolution, Pueo, Titan (rocket family), 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

We present observations of Titan taken on November 17, 2000, with the near-infrared spectro-imaging system OASIS, mounted downstream of the CFHT/PUEO adaptive optics system. We have spatially resolved Titan's disk at Greatest Eastern Elongation. Our spectra cover the 0.86– 1.02 μ m range with a spectral resolution of 1800. By studying Titan at these wavelengths, we have recovered several pieces of information on the vertical and latitudinal structure of the atmosphere and surface of the satellite. The observing conditions were sufficiently good (AO-corrected seeing of 0.34”) so as to allow us to separate the disk into 7 independent elements. From the flux contained in the 0.890 μ m methane band, we find that at higher altitudes on Titan, the North–South asymmetry is undergoing changes with respect to previous years when the South was much brighter than the North. This asymmetry still prevails in the troposphere, but at higher levels the well-known “Titan smile”—previously reported—disappears. We believe that we even have evidence for a reversal. The year 2000 may then represent the beginning of a seasonal change in Titan's haze distribution in the near-infrared, something which has been confirmed since but was not visible in the previous years. By comparing regions on Titan's disk with similar surface and stratospheric characteristics, we find an differences in the latitudinal distribution of the aerosol content in the intermediate altitude levels. Reflectivity measurements derived in the 0.94 μ m window (and hence pertaining to the surface conditions) show that the equatorial regions of the leading side are brighter than the surrounding areas, due to the presence of the large bright zone observed since 1994. Given our spatial resolution, we find this region to be 6% brighter than northern latitudes, 7% brighter than the South pole and in total we have a contrast of 9% between the darker and the brighter areas distinguishable on our images. The 0.94 μ m methane window yields a geometric albedo of about 0.26 for the bright center of Titan's disk. This region is affected by a strong H 2 O telluric absorption and therefore we could not derive any precise information on the surface composition from the original spectrum. We have, however, been able to correct for the telluric lines by using a stellar spectrum taken just before our Titan observations. We were then able to apply our radiative transfer code and after modeling surface albedo values of about 0.37 and 0.29 for the brightest and darkest areas respectively were found. We investigate possible surface components, compatible with our data, such as water ice, hydrocarbon liquid, tholin deposits or silicates.

Published
2005
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