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151. Venus Express mission

Author: Olivier Witasse, D. V. Titov, Håkan Svedhem, and Fredric W. Taylor
Subjects: Atmospheric Science, Solar System, Soil Science, Venus, Aquatic Science, Oceanography, Astrobiology, Atmosphere of Venus, Geochemistry and Petrology, Planet, Earth and Planetary Sciences (miscellaneous), Earth-Surface Processes, Water Science and Technology, Radio Science, Ecology, biology, Paleontology, Forestry, Mars Exploration Program, biology.organism_classification, Solar wind, Geophysics, Space and Planetary Science, Asteroid, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, Geology
Abstract: [1] Venus Express is well and healthy and has now been providing exciting new data from Venus, our nearby twin planet, for over 2 years. Many of the new results are presented and discussed in the subsequent papers in this special section. The overall scientific objective of Venus Express is to carry out a detailed study of the atmosphere of Venus, including the interaction of the upper atmosphere with the solar wind and the interaction of the lowest part of the atmosphere with the surface of the planet. In addition, the plasma environment and magnetic fields as well as some aspects of the surface of the planet are addressed. For the first time, investigations make systematic use of the transparent infrared spectral windows in order to probe the atmosphere in four dimensions: three spatial dimensions plus time. The spacecraft design is taken from Mars Express with some modifications necessary owing to the specific environment around Venus. The payload is composed of three spectrometers, a camera, a magnetometer, an instrument for detecting energetic particles, and a radio science package. The orbit is polar and highly elliptic, with a pericenter altitude of about 200 km over the northern polar region and an apocenter altitude of 66,000 km. Presently, the coverage of the southern hemisphere is very good, but important gaps still do exist. The coverage of the northern hemisphere is much less dense. Venus Express is a part of the European Space Agency's program for the exploration of the inner solar system, which includes missions to study the Sun, Mercury, Venus, the Moon, Mars, and comets and asteroids.
Published: 2009
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152. Solar System Ionospheres

Author: Arvydas J. Kliore, Michael Mendillo, Thomas E. Cravens, Julianne I. Moses, Olivier Witasse, Andrew F. Nagy, and T. K. Breus
Subjects: Physics, Solar System, Coupling (physics), Neutral atmosphere, Planetary science, Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Plasma, Ionosphere, Physics::Geophysics, Computational physics
Abstract: This article reviews our understanding of the ionospheres in the solar system. It provides some basic information on the sources and sinks of the ionospheric plasma, its dynamics, the energetics and the coupling to the neutral atmosphere. Ionospheres in the solar system are reviewed and comparative ionospheric topics are discussed.
Published: 2009
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153. Venus express: Highlights of the nominal mission

Author: J. A. Sauvaud, Vittorio Formisano, W. J. Markiewicz, Olivier Witasse, S. Barabash, Alexander S. Fedorov, Bernd Häusler, Jörn Helbert, Håkan Svedhem, P. Drossart, Jean-Loup Bertaux, Martin Pätzold, Fredric W. Taylor, D. V. Titov, D. Nevejans, Jean-Claude Gérard, Giuseppe Piccioni, R. Hoofs, Agustín Sánchez-Lavega, T. Zhang, Oleg Korablev, Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Space Research Institute of the Russian Academy of Sciences (IKI), Russian Academy of Sciences [Moscow] (RAS), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA), University of Oxford, Swedish Institute of Space Physics [Uppsala] (IRF), 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), 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), Istituto di Fisica dello Spazio Interplanetario (IFSI), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Universität der Bundeswehr München [Neubiberg], Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Rhenish Institute for Environmental Research (RIU), University of Cologne, Istituto di Astrofisica Spaziale e Fisica cosmica - Roma (IASF-Roma), Istituto Nazionale di Astrofisica (INAF), Centre d'étude spatiale des rayonnements (CESR), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-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 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), Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), Laboratoire de Physique Atmosphérique et Planétaire (LPAP), Université de Liège, Universidad del Pais Vasco / Euskal Herriko Unibertsitatea [Espagne] (UPV/EHU), DLR Institute of Planetary Research, German Aerospace Center (DLR), European Space Astronomy Centre (ESAC), Max Planck Institute for Solar System Research (MPS), European Space Agency (ESA), University of Oxford [Oxford], Consiglio Nazionale delle Ricerche (CNR), 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), and Université Fédérale Toulouse Midi-Pyrénées
Subjects: [PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Polar orbit, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Venus, 01 natural sciences, 7. Clean energy, Observations and explorations of Venus, Astrobiology, Planet, 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Radio Science, biology, Astronomy, Astronomy and Astrophysics, biology.organism_classification, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Planetary science, 13. Climate action, Space and Planetary Science, Sidereal time, Space Science, Geology
Abstract: International audience; Venus Express is the first European (ESA) mission to the planet Venus. Its main science goal is to carry out a global survey of the atmosphere, the plasma environment, and the surface of Venus from orbit. The payload consists of seven experiments. It includes a powerful suite of remote sensing imagers and spectrometers, instruments for in-situ investigation of the circumplanetary plasma and magnetic field, and a radio science experiment. The spacecraft, based on the Mars Express bus modified for the conditions at Venus, provides a versatile platform for nadir and limb observations as well as solar, stellar, and radio occultations. In April 2006 Venus Express was inserted in an elliptical polar orbit around Venus, with a pericentre height of ∼250 km and apocentre distance of ∼66000 km and an orbital period of 24 hours. The nominal mission lasted from June 4, 2006 till October 2, 2007, which corresponds to about two Venus sidereal days. Here we present an overview of the main results of the nominal mission, based on a set of papers recently published in Nature, Icarus, Planetary and Space Science, and Geophysical Research Letters.
Published: 2009
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154. Exospheric signatures of alkali abundances in Europa's regolith

Author: Olivier Witasse, François Leblanc, Robert E. Johnson, Fabrice Cipriani, European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), INAF - Osservatorio Astronomico di Trieste (OAT), Istituto Nazionale di Astrofisica (INAF), HELIOS - 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), Department of Materials Science and Engineering [Charlottesville] (MS), University of Virginia [Charlottesville], Agence Spatiale Européenne = European Space Agency (ESA), and University of Virginia
Subjects: 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Sodium, Potassium, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Mineralogy, chemistry.chemical_element, 01 natural sciences, Regolith, symbols.namesake, 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, Europa Orbiter, Observable, Alkali metal, Galilean moons, Geophysics, chemistry, 13. Climate action, symbols, General Earth and Planetary Sciences, Europa, Exosphere
Abstract: International audience; The sodium and potassium exospheres of Europa are described as well as the variations of the Na/K ratio from Europa's surface up to about 20 Europa radii. Observations carried out by M. E. Brown (2001) are used to constrain the Na and K source terms. We find that an average source rates ratio of 17 ± 2 at the surface and loss rates ratio of 26 ± 2 reproduce well the observations. These values are consistent with the conclusions by R. E. Johnson et al. (2002) on its most probable origin. Moreover, we here show that a local increase of the surface Na/K ratio by a factor 2 in a 20° × 30° wide region should induce an observable exospheric signature between 80 and 300 km above the surface. Therefore simultaneous observations of sodium and potassium from an Europa orbiter would allow one to derive important properties of the surface and subsurface of the Galilean moon.
Published: 2009
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155. Dayglow on Mars: Kinetic modelling with SPICAM UV limb data

Author: Guillaume Gronoff, C. Simon, Jean-Loup Bertaux, Olivier Witasse, François Leblanc, Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), 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), 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), and European Space Agency (ESA)-European Space Agency (ESA)
Subjects: 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Mars, Venus, Astrophysics, Atmospheric sciences, 01 natural sciences, Transport modelling, symbols.namesake, 0103 physical sciences, Upper atmosphere, Emission spectrum, Mars Express, Ionosphere, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Physics, biology, Airglow, Astronomy and Astrophysics, Mars Exploration Program, Atmosphere of Mars, biology.organism_classification, SPICAM, 13. Climate action, Space and Planetary Science, symbols, Dayglow, Thermosphere, Titan (rocket family)
Abstract: The UV spectrometer experiment SPICAM onboard ESA Mars Express has been orbiting Mars since December 2003. We present here some comparisons between airglow data that have been newly interpreted with the advanced kinetic model Trans-Mars. A series of numerical one-dimensional kinetic models, in the Trans-* family [Lilensten, J., Blelly. P.L., 2002. The TEC and F2 parameters as tracers of the ionosphere and thermosphere. J. Atmos. Solar-Terrestrial Phys. 64, 775–793] has been developed over the last years to take into account of airglow processes and yield altitude line profiles in planetary upper atmospheres (Earth, Venus, Titan and Mars). Trans-Mars is the last evolution of these simulations, applied to Mars. Electron and photon cross sections have been recently updated. The computed model line profiles are comparable to those of Fox and Dalgarno [1979b. Ionization, luminosity, and heating of the upper atmosphere of Mars. J. Geophys. Res. 84, 7315–7333] and Shematovich et al. [2008. Monte Carlo model of electron transport for the calculation of Mars dayglow emissions. J. Geophys. Res. (Planets) 113(E12), 2011]. Nearly 70000 limb UV spectra recorded by SPICAM between October 2004 and May 2006 are analysed in order to obtain altitude emission profiles on the main dayglow emissions. A variable point spread function (PSF) determined statistically throughout the wavelength range is used to estimate precisely the intensity of the airglow. This includes the Cameron bands ( a 3 Π - X 1 Σ ) of CO, the CO 2 + ultraviolet doublet ( B 2 Σ u + - X 2 Π g ) at 289.0 nm and the oxygen emission at 297.2 nm. Instrumental uncertainties of the emissions remain under 15%. Five groups of comparable orbits are selected to prepare for the data interpretation. The seasonal and solar activity effects on the dayside CO ‘Cameron Bands’, CO 2 + and OI(2972 A) emissions are discussed in light of previous studies. These emissions exhibit for equatorial latitudes two maxima of intensity for L S = 140 ∘ and 290 ∘ (around Mars’ perihelion) and one local minimum at L S ∼ 40 ∘ . The peak at L S = 140 ∘ is corroborated by the neutral density profiles shown by Forget et al. [2008. The density and temperatures of the upper martian atmosphere measured by stellar occultations with Mars Express SPICAM. J. Geophys. Res., 1–25, submitted for publication] using SPICAM stellar occultation mode; these authors linked this sudden increase to a dust storm covering a large part of the planet, a quite unexpected event at this time of the year. A first comparison of altitude profiles of emission lines between data and the kinetic transport model shows a very similar shape and altitude peak when Viking CO 2 densities are divided by a factor 3 and uncertainties in the cross sections are taken into account. Overall intensities are, however, overestimated by our model by 25% on average for Cameron and CO 2 + emissions. The limits of the model and further improvements both on the data analysis and on the model are presented.
Published: 2009
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156. Observations of aurorae by SPICAM ultraviolet spectrograph on board Mars Express: Simultaneous ASPERA-3 and MARSIS measurements

Author: F. Leblanc, Ali Safaenili, Jasper Halekas, Hans Nilsson, Yoshifumi Futaana, J. D. Winningham, Wlodek Kofman, David Brain, Jeremie Mouginot, Olivier Witasse, Jean Lilensten, R. A. Frahm, J. L. Bertaux, Mats Holmström, and Rickard Lundin
Subjects: Atmospheric Science, Electron spectrometer, 010504 meteorology & atmospheric sciences, Soil Science, MARSIS, Astrophysics, Aquatic Science, Oceanography, 01 natural sciences, Atmosphere, Geochemistry and Petrology, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Martian, Physics, Ecology, Total electron content, Paleontology, Forestry, Geophysics, Mars Exploration Program, Atmosphere of Mars, 13. Climate action, Space and Planetary Science, Ionosphere
Abstract: We present a new set of observations of Martian aurorae obtained by Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) on board Mars Express (MEX). Using nadir viewing, several auroral events have been identified on the Martian nightside, all near regions of crustal magnetic fields. For most of these events, two to three consecutive events with variable intensities and separated by a few seconds to several tens of seconds have been observed, whereas simultaneous observations with Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) and Analyzer of Space Plasma and Energetic Atoms (ASPERA-3) have been possible. In this paper, we present the data set for these events and discuss the possible correlation between the measured UV emission by SPICAM, the measured downward and/or upward flux of electrons by ASPERA-3 and the total electron content recorded by MARSIS. Despite the limited coverage of SPICAM ultraviolet spectrograph (UVS) on the Martian nightside (essentially in regions of high crustal magnetic fields), there is however a very good correlation between the regions with the locally smallest probability to be on closed crustal magnetic field lines, as derived from Mars Global Surveyor/Electron Reflectometer (MGS/MAG-ER), and the position of an aurora event. This suggests that the crustal magnetic fields, when organized into cusp-like structure, can trigger the few aurorae identified by SPICAM UVS. It confirms also the good probability, in the cases where SPICAM UVS measured UV emissions, that the increase in the measured total electron content by MARSIS and the simultaneous measured precipitating electron flux by the ASPERA-3/Electron Spectrometer may be related to each other.
Published: 2008
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157. Optical estimation of auroral ion upflow: 2. A case study

Author: Stephen B. Mende, Olivier Witasse, Hans Gleisner, M. Zettergren, I. Azeem, G. G. Sivjee, Marcos Diaz, Joshua Semeter, and Pierre-Louis Blelly
Subjects: Atmospheric Science, Plasma parameters, Incoherent scatter, Soil Science, Aquatic Science, Oceanography, law.invention, Ion, Optics, Geochemistry and Petrology, law, Earth and Planetary Sciences (miscellaneous), Radar, Earth-Surface Processes, Water Science and Technology, Physics, Ecology, business.industry, Paleontology, Estimator, Forestry, Plasma, Wavelength, Geophysics, Space and Planetary Science, Physics::Space Physics, Ionosphere, business
Abstract: [1] This work presents a detailed multi-instrument and modeling case study of an ion upflow event occurring over the Sondrestrom incoherent scatter radar on 17 February 2001. This case study is used to demonstrate the effectiveness of a previously developed optical estimator of ion upflow. The optical estimator of ion upflow is applied in a two step process: (1) near-infrared (NIR) optical observations in the 700–850 nm wavelength range are inverted to reconstruct the energy distribution of precipitating electrons then (2) the reconstructed precipitation is applied to a combined fluid-kinetic model of the ionosphere (TRANSCAR) to estimate the plasma response to the auroral particles. Plasma parameters estimated by this procedure are compared with plasma parameters derived from incoherent scatter radar data recorded during the event and are shown to be in reasonably good agreement. However, this study highlights an important limitation of the estimation technique, the lack of a direct measure of the ambient ionospheric state (nighttime plasma density). Means for addressing this limitation are discussed and may eventually allow for estimation of ionospheric state parameters under certain conditions by using optical sensors.
Published: 2008
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158. A coordinated campaign of Venus ground-based observations and Venus Express measurements

Author: Emmanuel Lellouch, Olivier Witasse, Observatoire de Paris, Université Paris sciences et lettres (PSL), 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), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and Research and Scientific Support Department, ESA-ESTEC (RSSD)
Subjects: biology, Space and Planetary Science, Astronomy and Astrophysics, Venus, biology.organism_classification, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Geology, Astrobiology
Abstract: International audience; Not Available
Published: 2008
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159. The Huygens scientific data archive: Technical overview

Author: Mark Leese, G. Israel, Lisa McFarlane, Bobby Kazeminejad, Michael K. Bird, Reta Beebe, Axel Hagermann, Roland Trautner, B. Hathi, R. Dutta-Roy, Joe Zender, Jean-Pierre Lebreton, Cyril Pennanech, Lyn R. Doose, J. A. Haberman, Giacomo Colombatti, Piero Leon Stoppato, Joe Wheadon, Fernando Simões, Olivier Witasse, Marty Tomasko, David H. Atkinson, Jaime E. Demick-Montelara, Miguel Pérez-Ayúcar, David Heather, Francesca Ferri, C. See, Lyle Huber, Dennis L. Matson, Alessio Aboudan, Jean Francis Brun, John C. Zarnecki, Marcello Fulchignoni, Hasso B. Niemann, European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), Department of Astronomy [Las Cruces], New Mexico State University, Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, Planetary and Space Sciences Research Institute [Milton Keynes] (PSSRI), Centre for Earth, Planetary, Space and Astronomical Research [Milton Keynes] (CEPSAR), The Open University [Milton Keynes] (OU)-The Open University [Milton Keynes] (OU), European Space Operations Center (ESOC), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' (CISAS), Universita degli Studi di Padova, Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-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), NASA Goddard Space Flight Center (GSFC), German Space Operations Center (GSOC), Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), 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), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Department of Electrical and Computer Engineering [Moscow, USA], University of Idaho [Moscow, USA], Agence Spatiale Européenne = European Space Agency (ESA), NASA-California Institute of Technology (CALTECH), and Università degli Studi di Padova = University of Padua (Unipd)
Subjects: Scientific instrument, 0303 health sciences, Astronomy and Astrophysics, Cassini/Huygens mission, 01 natural sciences, Planetary Data System, Radio telescope, 03 medical and health sciences, symbols.namesake, Interferometry, Data acquisition, Planetary science, Space and Planetary Science, [SDU]Sciences of the Universe [physics], 0103 physical sciences, Very-long-baseline interferometry, symbols, Data archiving, Titan (rocket family), Titan, 010303 astronomy & astrophysics, Geology, 030304 developmental biology, Remote sensing
Abstract: The Cassini/Huygens mission was launched in October 1997, and during the third orbit around Saturn, the Huygens probe was released on course to enter Titan's atmosphere. During the descent, six science instruments provided in situ and remote sensing measurements of Titan's atmosphere and surface. Doppler tracking was performed with two Earth-based radio telescopes, and a Very Long Base Interferometry (VLBI) experiment was carried out. Data acquisition began around 1500 km altitude and continued throughout the 2 h and 30 min descent and for 1 h and 12 min after landing. This unique set of data is available in the ESA Planetary Science Archive (PSA) and mirror imaged in the NASA Planetary Data System (PDS). This paper presents an overview of the process the Huygens Data Archiving Working Group followed to develop and ingest the data set. A description of the data sets is also given.
Published: 2008
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160. Sodium recycling at Europa: what do we learn from the sodium cloud variability ?

Author: Olivier Witasse, Fabrice Cipriani, Robert E. Johnson, François Leblanc, European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA), INAF - Osservatorio Astronomico di Trieste (OAT), Istituto Nazionale di Astrofisica (INAF), 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), Engineering Physics Program [Charlottesville], University of Virginia, European Space Agency (ESA), and University of Virginia [Charlottesville]
Subjects: exosphere-surface coupling, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Materials science, animal structures, 010504 meteorology & atmospheric sciences, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Sodium, Analytical chemistry, chemistry.chemical_element, Plasma, Electron, 01 natural sciences, Ion, Geophysics, chemistry, 13. Climate action, Sputtering, Desorption, 0103 physical sciences, General Earth and Planetary Sciences, Redistribution (chemistry), Atomic physics, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Exosphere
Abstract: International audience; We study the ejection of sodium atoms from Europa's surface by both magnetospheric ion and electron sputtering and desorption stimulated by UV solar photons. The depletion of the surface by ejection and its enrichment by redeposition of sodium atoms are described. The redistribution of sodium atoms at the surface induced by photo-stimulated desorption from the dayside and by sputtering ejection from the trailing hemisphere cannot explain the observed variation of the Na emission brightness. However, a transient increase of the sputtering rate due to a plasma injection may explain such an increase. The relationship between the sodium surface content and the sodium exosphere are also discussed.
Published: 2008
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161. Venus Express—The first European mission to Venus

Author: Jean-Pierre Lebreton, Detlef Koschny, H. Eggel, M. Warhaut, D. McCoy, Martin Pätzold, T. L. Zhang, Fredric W. Taylor, Giuseppe Piccioni, Oleg Korablev, Jean-Loup Bertaux, Pierre Drossart, T. Schirmann, D. Nevejans, A. Clochet, J. Rodriguez-Canabal, Håkan Svedhem, Bernd Häusler, E. Lellouch, M. Coradini, Andrea Accomazzo, W. J. Markiewicz, Olivier Witasse, S. Barabash, Vittorio Formisano, D. V. Titov, J. Fabrega, 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), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Space Research Institute of the Russian Academy of Sciences (IKI), Russian Academy of Sciences [Moscow] (RAS), Swedish Institute of Space Physics [Kiruna] (IRF), 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), Istituto di Fisica dello Spazio Interplanetario (IFSI), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Universität der Bundeswehr München [Neubiberg], Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Institute for Geophysics and Meteorology [Köln] (IGM), University of Cologne, Istituto di Astrofisica Spaziale e Fisica cosmica - Roma (IASF-Roma), Istituto Nazionale di Astrofisica (INAF), Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), University of Oxford, European Space Operations Center (ESOC), ASTRIUM, and EADS - European Aeronautic Defense and Space
Subjects: Engineering, 010504 meteorology & atmospheric sciences, Polar orbit, Venus, 01 natural sciences, 7. Clean energy, Astrobiology, Atmosphere of Venus, Atmosphere, Planet, 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], biology, Payload, business.industry, Astronomy, Astronomy and Astrophysics, biology.organism_classification, Solar wind, 13. Climate action, Space and Planetary Science, Sidereal time, [SDU]Sciences of the Universe [physics], business
Abstract: Venus Express is the first European mission to planet Venus. The mission aims at a comprehensive investigation of Venus atmosphere and plasma environment and will address some important aspects of the surface physics from orbit. In particular, Venus Express will focus on the structure, composition, and dynamics of the Venus atmosphere, escape processes and interaction of the atmosphere with the solar wind and so to provide answers to the many questions that still remain unanswered in these fields. Venus Express will enable a breakthrough in Venus science after a long period of silence since the period of intense exploration in the 1970s and the 1980s. The payload consists of seven instruments. Five of them were inherited from the Mars Express and Rosetta projects while two instruments were designed and built specifically for Venus Express. The suite of spectrometers and imaging instruments, together with the radio-science experiment, and the plasma package make up an optimised payload well capable of addressing the mission goals to sufficient depth. Several of the instruments will make specific use of the spectral windows at infrared wavelengths in order to study the atmosphere in three dimensions. The spacecraft is based on the Mars Express design with minor modifications mainly needed to cope with the thermal environment around Venus, and so a very cost-effective mission has been realised in an exceptionally short time. The spacecraft was launched on 9 November 2005 from Baikonur, Kazakhstan, by a Russian Soyuz-Fregat launcher and arrived at Venus on 11 April 2006. Venus Express will carry out observations of the planet from a highly elliptic polar orbit with a 24-h period. In 3 Earth years (4 Venus sidereal days) of operations, it will return about 2 Tbit of scientific data. Telecommunications with the Earth is performed by the new ESA ground station in Cebreros, Spain, while a nearly identical ground station in New Norcia, Australia, supports the radio-science investigations. © 2007 Elsevier Ltd. All rights reserved.
Published: 2007
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162. Analysis and modelling of SPICAM data onboard Mars Express

Author: Cyril Simon, Olivier Witasse, François Leblanc, Jean Lilensten, Jeremie Mouginot, Wlodek Kofman, Jean-Loup Bertaux, Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), 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), and European Space Agency (ESA)-European Space Agency (ESA)
Subjects: [SDU]Sciences of the Universe [physics], Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics
Abstract: EGU2007-A-06650; For more than three years SPICAM UV spectrometer onboard ESA mission Mars Express has been successfully monitoring the upper atmosphere of Mars in the range 118-320 nm. We will present the preliminary results concerning the numerical modelling of Mars' dayglow through the computation of UV emission lines such as CO Cameron bands and N2 Vegard-aplan bands. The theory underlying this modelling uses Boltzmann's statistical kinetic and fluid approaches to yield electron/ion density and temperature profiles as a function of altitude as well as observable variables like the volume emission rates. The outputs of the model can be directly compared to the processed SPICAM data. A few characteristic orbits are then chosen for analysis in order to compare with the numerical modelling.
Published: 2007

163. Venus Express science planning

Author: Martin Pätzold, Joe Zender, Pierre Drossart, D. V. Titov, Bernd Häusler, R. Hoofs, D. Merritt, D. Trillard, Vittorio Formisano, Andrea Accomazzo, M. Janvier, Oleg Korablev, A. Clochet, Håkan Svedhem, T. L. Zhang, M. Sweeney, Giuseppe Piccioni, W. J. Markiewicz, Olivier Witasse, S. Barabash, D. Nevejans, Detlef Koschny, Jean-Loup Bertaux, Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Space Research Institute of the Russian Academy of Sciences (IKI), Russian Academy of Sciences [Moscow] (RAS), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA), Swedish Institute of Space Physics [Kiruna] (IRF), 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 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), Istituto di Fisica dello Spazio Interplanetario (IFSI), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Universität der Bundeswehr München [Neubiberg], Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Institute for Geophysics and Meteorology [Köln] (IGM), University of Cologne, Istituto di Astrofisica Spaziale e Fisica cosmica - Roma (IASF-Roma), Istituto Nazionale di Astrofisica (INAF), Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), European Space Operations Center (ESOC), EADS Innovation Works [Toulouse], EADS - European Aeronautic Defense and Space, Max-Planck-Institut für Sonnensystemforschung (MPS), European Space Agency (ESA), Consiglio Nazionale delle Ricerche (CNR), and EADS Astrium SAS
Subjects: [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Venus Express, 010504 meteorology & atmospheric sciences, biology, Computer science, Process (engineering), Payload, Astronomy and Astrophysics, Timeline, Venus, Plan (drawing), biology.organism_classification, 01 natural sciences, Occultation, Space and Planetary Science, Planet, [SDU]Sciences of the Universe [physics], 0103 physical sciences, Systems engineering, Orbit (dynamics), Science planning, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Remote sensing
Abstract: Venus Express is the first European mission to the planet Venus. Its payload consists of seven instruments and will investigate the atmosphere, the plasma environment, and the surface of Venus from orbit. Science planning is a complex process that takes into account requests from all experiments and the operational constraints. The planning of the science operations is based on synergetic approach to provide good coverage of science themes derived from the main mission goals. Typical observations in a single orbit—so-called “science cases” are used to build the mission science activity plan. The nominal science mission (from June 4, 2006 till October 2, 2007) is divided in nine phases depending on observational conditions, occurrences of the solar and Earth occultation, and particular science goals. The observation timelines for each phase were developed in a coordinated way to optimize the payload activity, maximize the overall mission science return, and to fit into the available mission budgets.
Published: 2007
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164. Modelling dications in the diurnal ionosphere of venus

Author: Olivier Witasse, C. Simon, Christian Alcaraz, Odile Dutuit, Guillaume Gronoff, Roland Thissen, Jean Lilensten, Laboratoire de Chimie Physique D'Orsay (LCPO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-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), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), and European Space Agency (ESA)-European Space Agency (ESA)
Subjects: 010504 meteorology & atmospheric sciences, planets and satellites, Venus, Astrophysics, 01 natural sciences, 7. Clean energy, Ion, Astrobiology, symbols.namesake, Ionization, 0103 physical sciences, individual, 010303 astronomy & astrophysics, Venus -atmospheric effects -Sun, Electron ionization, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Physics, biology, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astronomy and Astrophysics, Mars Exploration Program, UV radiation -space vehicles, biology.organism_classification, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Physics::Space Physics, instruments, symbols, Terrestrial planet, Astrophysics::Earth and Planetary Astrophysics, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Ionosphere, Atomic physics, Titan (rocket family)
Abstract: International audience; Context.Previous studies have shown that doubly-charged positive ions, including molecular ions, can have detectable densities in the ionospheres of Mars, Titan, and the Earth. Aims.In the present paper, we continue our approach by modelling the Venusian ionosphere. The neutral atmosphere of Venus has a similar composition to the ones encountered in the other terrestrial planets, with carbon dioxide (as on Mars), nitrogen (as on Earth and Titan), and atomic oxygen (as on Earth). Methods. We computed the doubly-charged positive ion production through photoionisation (primary production) and electron impact ionisation (secondary production). We computed the densities under the photochemical equilibrium assumption. Results. We predict a ${\rm CO_2}^$ layer centred around $140~{\rm km}$ altitude with a density reaching 30 dications per ${\rm cm}^{3}$ in active solar conditions and a ${\rm N_2}^$ layer centred around a $140{-}150~{\rm km}$ altitude with density reaching $0.3~{\rm cm}^$. We find good agreement between the modelled ${\rm O}^$ densities and Pioneer Venus Orbiter measurements. Finally, we investigate the problem of possible detection of these ions by the European spacecraft Venus Express. Conclusions. Although molecular doubly-charged positive ion densities are low, these ions cannot be considered as negligible compared to other minor ion species. Their detection should be possible in the future through remote sensing or in-situ methods including ion mass spectrometry and UV spectroscopy.
Published: 2007
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165. Habitat of early life: Solar X-ray and UV radiation at Earth's surface 4-3.5 billion years ago

Author: N. F. Arnold, Jorge Sanz-Forcada, Olivier Witasse, Ingrid Cnossen, Tanja Zegers, and Fabio Favata
Subjects: Atmospheric Science, Ozone, Extinction (astronomy), Soil Science, Flux, FOS: Physical sciences, Astrophysics, Aquatic Science, Radiation, Oceanography, Atmosphere, chemistry.chemical_compound, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Absorption (electromagnetic radiation), Earth-Surface Processes, Water Science and Technology, Physics, Ecology, Astrophysics (astro-ph), Paleontology, Forestry, Wavelength, Geophysics, chemistry, Space and Planetary Science, Water vapor
Abstract: Solar X-ray and UV radiation (0.1-320 nm) received at Earth's surface is an important aspect of the circumstances under which life formed on Earth. The quantity that is received depends on two main variables: the emission of radiation by the young Sun and its extinction through absorption and scattering by the Earth's early atmosphere. The spectrum emitted by the Sun when life formed, between 4 and 3.5 Ga, was modeled here, including the effects of flares and activity cycles, using a solar-like star that has the same age now as the Sun had 4-3.5 Ga. Atmospheric extinction was calculated using the Beer-Lambert law, assuming several density profiles for the atmosphere of the Archean Earth. We found that almost all radiation with a wavelength shorter than 200 nm is attenuated effectively, even by very tenuous atmospheres. Longer-wavelength radiation is progressively less well attenuated, and its extinction is more sensitive to atmospheric composition. Minor atmospheric components, such as methane, ozone, water vapor, etc., have only negligible effects, but changes in CO2 concentration can cause large differences in surface flux. Differences due to variability in solar emission are small compared to this. In all cases surface radiation levels on the Archean Earth were several orders of magnitude higher in the 200-300 nm wavelength range than current levels in this range. That means that any form of life that might have been present at Earth's surface 4-3.5 Ga must have been exposed to much higher quantities of damaging radiation than at present., Comment: 19 pages, published by JGR-Planets
Published: 2007
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166. Une revue des ions doublement chargés dans les ionosphères planétaires

Author: Jean Lilensten, Cyril Simon, Olivier Witasse, Guillaume Gronoff, Roland Thissen, Odile Dutuit, Christian Alcaraz, Soldi-Lose, H., 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), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), Laboratoire de Chimie Physique D'Orsay (LCPO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut für Chemie, and Der Technischen Universität Berlin
Subjects: ComputingMilieux_MISCELLANEOUS
Abstract: National audience
Published: 2006

167. New evaluation of N+, N2+ and N2++ ion-molecule reactions relevant for the chemistry of Titan's ionosphere

Author: Christian Alcaraz, Odile Dutuit, Roland Thissen, Soldi-Lose, H., Jan Zabka, Francheschi, P., Olivier Witasse, Cyril Simon, Jean Lilensten, Laboratoire pour l'Utilisation du Rayonnement Electromagnétique (LURE) (LURE), Centre Universitaire Paris-Sud, Laboratoire de Chimie Physique D'Orsay (LCPO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut für Chemie, Der Technischen Universität Berlin, J. Heyrovský Institute of Physical Chemistry, J. Heyrovsky Institute of Physical Chemistry, Dipartimento di Fisica [Povo], Università degli Studi di Trento (UNITN), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), Laboratoire de Planétologie de Grenoble (LPG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics
Abstract: EGU05-A-08277; International audience; In the next weeks and years, the Cassini-Huygens mission will bring some new discoveries on the upper atmosphere of Titan. In this context, it is important to well caracterize the ion production and decay processes for a good understanding of the ionosphere chemistry. In Titan's ionosphere, the dissociative and non-dissociative photoionisation of N2 by solar vacuum ultra-violet are the principal processes responsible for the production of N+, N+2 and N++ 2 primary ions during the day. We will first discuss how these processes can lead to species with internal excitation (electronic and/or vibrational) and also with translational energy [1-3]. The subsequent reactions of these primary ions have been measured in laboratory experiments [1,4] and compared to the literature values [5-7] used in ionospheric models. We will show how the rate constants and the branching ratios to secondary products can be strongly affected by the primary ion internal and translational energy. Consequences on the ionospheric models are discussed.
Published: 2006

168. Overview of the coordinated ground-based observations of Titan during the Huygens mission

Author: Theodor Kostiuk, Glen Langston, William M. Folkner, Olivier Witasse, Emily L. Schaller, Christophe O. Laux, Jean-Pierre Lebreton, R. Dutta-Roy, Sergei Pogrebenko, Hayley Bignall, Frank D. Ghigo, Arpad Szomoru, Robert M. Campbell, Thierry Magin, Huib Jan van Langevelde, Máté Ádámkovics, Ralph D. Lorenz, Cormac Reynolds, John Reynolds, Bonnie J. Buratti, Robert J. Sault, Ari Mujunen, Imke de Pater, M. A. Garrett, Stephen M. Parsley, Jonathan D. Romney, Eric Gendron, Thierry Blancquaert, Timothy A. Livengood, Anastasios Tzioumis, Chad Trujillo, Michael E. Brown, Robert A. Preston, Antonin Bouchez, Chris Phillips, Walter Brisken, Michael K. Bird, Sami W. Asmar, Bruno Sicardy, Mathieu Hirtzig, Jouko Ritakari, Steven Tingay, Anne Bourdon, C.G.M. van 't Klooster, Alberto Negrao, David Luz, Lise Caillault, I. M. Avruch, Richard Dodson, Henry G. Roe, Markus Hartung, Athena Coustenis, Leonid I. Gurvits, European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), RadioAstronomisches Institut [Bonn] (RAIUB), Rheinische Friedrich-Wilhelms-Universität Bonn, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Joint Institute for VLBI in Europe (JIVE ERIC), Australia Telescope National Facility (ATNF), Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), National Radio Astronomy Observatory [Green Bank] (NRAO), National Radio Astronomy Observatory (NRAO), National Radio Astronomy Observatory [Socorro] (NRAO), Metsähovi Radio Observatory, Aalto University, Swinburne University of Technology (Hawthorn campus), Observatorio Astronomico Nacional, Madrid, 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), 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), Observatório Astronómico de Lisboa, Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Laboratoire d'Énergétique Moléculaire et Macroscopique, Combustion (EM2C), Université Paris Saclay (COmUE)-Centre National de la Recherche Scientifique (CNRS)-CentraleSupélec, von Karman Institute for Fluid Dynamics (VKI), Agence Spatiale Européenne = European Space Agency (ESA), and CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Université Paris Saclay (COmUE)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Soil Science, Aquatic Science, Oceanography, 01 natural sciences, Wind speed, Radio telescope, symbols.namesake, Geochemistry and Petrology, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], Radio signal, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Remote sensing, Ecology, Lune, Paleontology, Forestry, Geophysics, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Physics::Space Physics, symbols, Astrophysics::Earth and Planetary Astrophysics, Titan (rocket family), Geology
Abstract: Coordinated ground-based observations of Titan were performed around or during the Huygens atmospheric probe mission at Titan on 14 January 2005, connecting the momentary in situ observations by the probe with the synoptic coverage provided by continuing ground-based programs. These observations consisted of three different categories: (1) radio telescope tracking of the Huygens signal at 2040 MHz, (2) observations of the atmosphere and surface of Titan, and (3) attempts to observe radiation emitted during the Huygens Probe entry into Titan's atmosphere. The Probe radio signal was successfully acquired by a network of terrestrial telescopes, recovering a vertical profile of wind speed in Titan's atmosphere from 140 km altitude down to the surface. Ground-based observations brought new information on atmosphere and surface properties of the largest Saturnian moon. No positive detection of phenomena associated with the Probe entry was reported. This paper reviews all these measurements and highlights the achieved results. The ground-based observations, both radio and optical, are of fundamental importance for the interpretation of results from the Huygens mission.
Published: 2006
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169. Origins of the Martian aurora observed by Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars (SPICAM) on board Mars Express

Author: Jasper Halekas, Olivier Witasse, R. A. Frahm, Jean Lilensten, François Leblanc, J. D. Winningham, David Brain, Pierre-Louis Blelly, Jean-Loup Bertaux, 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), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), Space Science and Engineering Division [San Antonio], Southwest Research Institute [San Antonio] (SwRI), Space Sciences Laboratory [Berkeley] (SSL), University of California [Berkeley] (UC Berkeley), University of California (UC)-University of California (UC), 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), Laboratoire de physique et chimie de l'environnement (LPCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), European Space Agency (ESA)-European Space Agency (ESA), University of California [Berkeley], University of California-University of California, and Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, FLUXES, 010504 meteorology & atmospheric sciences, Soil Science, Aquatic Science, Oceanography, 01 natural sciences, Astrobiology, PLASMA ACCELERATION, Atmosphere, CARBON-DIOXIDE, Geochemistry and Petrology, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), SPECTROMETER, RATES, Spectroscopy, 010303 astronomy & astrophysics, Spectrograph, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Martian, Physics, Ecology, IONOSPHERE, Airglow, MAGNETIC-FIELD, Paleontology, Forestry, Atmosphere of Mars, Mars Exploration Program, Geophysics, AIRGLOW, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], IONIZATION, Ionosphere
Abstract: International audience; On the 11 August 2004, the UV spectrograph Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars (SPICAM) on board Mars Express made the first observation of auroral-type emission on the Martian nightside. In this paper, we describe the results of a new analysis of the observed emission owing to a better calibration of SPICAM UV channel and the use of all spectral information obtained during this observation. Several possibilities for the origin of this emission are discussed. We discussed, in particular, the possible exact geometry of the observation and the possible origins of the Martian aurorae. The emissions measured by SPICAM ultraviolet spectrometer have most probably been produced by electrons with an energy distribution peaking at few tens of eV rather than by electron distributions peaking above 100 eV.
Published: 2006
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170. Stratospheric global winds on Titan at the time of Huygens descent

Author: Koji Murakawa, F. Schmülling, Timothy A. Livengood, David Luz, Olivier Witasse, David Buhl, Tilak Hewagama, Kelly E. Fast, T. Kostiuk, Alan T. Tokunaga, G. Sonnabend, J. Annen, Subaru Telescope, Universities Space Research Association, Washington (USRA), Physikalisches Institut, Universität zu Köln, NASA/Goddard Space Flight Center (NASA/GSFC), Department of Astronomy, University of Maryland, Max-Planck-Institut für Radioastronomie (MPIfR), Institute for Astronomy, University of Hawaii, 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), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and Research and Scientific Support Department, ESA-ESTEC (RSSD)
Subjects: Atmospheric Science, Soil Science, Atmospheric model, Aquatic Science, Oceanography, Atmospheric sciences, Wind speed, symbols.namesake, Geochemistry and Petrology, Stratopause, Observatory, Wind shear, Earth and Planetary Sciences (miscellaneous), Stratosphere, Earth-Surface Processes, Water Science and Technology, Ecology, Paleontology, Forestry, Geophysics, Space and Planetary Science, symbols, Titan (rocket family), Subaru Telescope, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Geology
Abstract: International audience; Measurements of stratospheric zonal winds on Titan were made in preparation for and during the time of the descent of the Huygens Probe into Titan's atmosphere on 14 January 2005. Fully resolved emission lines from ethane near 11.7 mum were measured on the east, center, and west positions on Titan using the NASA/GSFC Heterodyne Instrument for Planetary Wind And Composition, HIPWAC, mounted on the National Astronomical Observatory of Japan 8.2 m Subaru Telescope on Mauna Kea, Hawaii. Analysis of the Doppler shifts of the emission line shapes yielded mean prograde gas velocity ~60 +/- 65 m/s at altitudes below ~120 km (~5 mbar). This result is consistent with retrievals from the Huygens Doppler Wind Experiment and from other observations near this altitude range. Current spectral line shapes, however, differed significantly from those obtained in similar measurements on Subaru in 2004 and on the NASA IRTF in 1993-1996, which retrieved prograde zonal winds 190 +/- 90 m/s at 230 km (~0.4 mbar). The cores of the emission lines, which probe the high-altitude region, could not be fitted as before to retrieve wind directly using the accepted atmospheric model for Titan. They imply an approximately tenfold increase in ethane mole fraction (1.2 × 10-4) with strong wind shear above the stratopause, providing a potential probe of the lower mesosphere and possible evidence of temporal and spatial variability. Results contribute to coordinated measurements of winds by various techniques providing information on the altitude distribution of wind velocity in Titan's atmosphere from near the surface to the lower mesosphere.
Published: 2006
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171. Huygens entry emission: Observation campaign, results, and lessons learned

Author: Imke de Pater, Mark T. Lemmon, Ralph D. Lorenz, Olivier Witasse, Jean-Pierre Lebreton, Bonnie J. Burratti, S. Holmes, Keith S. Noll, Thierry Blancquaert, Franck Mazoue, and Henry G. Roe
Subjects: Atmospheric Science, Ecology, Spacecraft, business.industry, Paleontology, Soil Science, Forestry, Aquatic Science, Oceanography, Astrobiology, symbols.namesake, Geophysics, Space and Planetary Science, Geochemistry and Petrology, Atmospheric entry, Earth and Planetary Sciences (miscellaneous), symbols, business, Titan (rocket family), Geology, Earth-Surface Processes, Water Science and Technology
Abstract: [1] An attempt was made to observe from Earth the emission from the shock layer and “meteor trail” formed during the Huygens probe's hypersonic entry into Titan's atmosphere. Although many observations were wiped out by weather or in-orbit failure, two observations constrain the emission from the entry. Several important lessons for future observations of spacecraft and other entries can be drawn.
Published: 2006
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172. Characterization of zonal winds in the stratosphere of Titan with UVES: 2. Observations coordinated with the Huygens Probe entry

Author: Olivier Witasse, T. Civeit, L. M. Lara, Timothy A. Livengood, A. Kaufer, Jean-Pierre Lebreton, T. Kostiuk, Francesca Ferri, D. Gautier, Regis Courtin, David Luz, 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), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Research and Scientific Support Department, ESA-ESTEC (RSSD), European Southern Observatory, Università degli Studi di Padova = University of Padua (Unipd), Instituto de Astrofisica de Andalucia, CSIC (IAA), and NASA/Goddard Space Flight Center (NASA/GSFC)
Subjects: Atmospheric Science, Soil Science, Aquatic Science, Oceanography, Spectral line, law.invention, Telescope, Atmosphere, symbols.namesake, Geochemistry and Petrology, law, Earth and Planetary Sciences (miscellaneous), Image resolution, Stratosphere, Earth-Surface Processes, Water Science and Technology, Very Large Telescope, Ecology, Paleontology, Forestry, Geophysics, Geodesy, Wavelength, Space and Planetary Science, symbols, Titan (rocket family), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Geology
Abstract: International audience; The Huygens Probe has successfully entered Titan's atmosphere and landed on its surface on 14 January 2005. With the aim of characterizing the zonal wind flow in Titan's stratosphere close to the time of entry, coordinated observations were carried out at the Very Large Telescope on the nights of 7, 12, 14, and 15 January. As in our previous investigation (Luz et al., 2005), we used the UVES instrument, mounted on the Kueyen-UT2 telescope, simultaneously achieving high spectral resolving power and high spatial resolution. The field has been derotated in order to align the 0.3-arcsec aperture perpendicularly to Titan's rotation axis. In this configuration, spatial information in the east-west direction is preserved in a set of spectra in the direction perpendicular to dispersion. We present measurements of zonal winds obtained with the technique of absolute accelerometry. The observations were made in the wavelength range 4200-6200 Å, probing between 115 and 280 km, with peak contributions at 200 and 170 km for the lower and upper parts of the domain. We detect prograde zonal winds with lower limits 46 and 53 ms-1 at these altitudes. These values are close to our previous measurements.
Published: 2006
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173. Martian dayglow as seen by the SPICAM UV spectrograph on Mars Express

Author: Jean Lilensten, François Leblanc, Olivier Witasse, Jean-Yves Chaufray, Jean-Loup Bertaux, 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), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA), and European Space Agency (ESA)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Solar zenith angle, Soil Science, Astrophysics, UPPER-ATMOSPHERE, Aquatic Science, Oceanography, MARINER 6, 01 natural sciences, Astrobiology, Atmosphere, ULTRAVIOLET SPECTROMETER EXPERIMENT, Geochemistry and Petrology, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), LYMAN-ALPHA, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Martian, Physics, SPECTROSCOPY, Ecology, IONOSPHERE, MAGNETIC-FIELD, Paleontology, Forestry, Lyman-alpha line, Scale height, Solar wind, Geophysics, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], SOLAR-WIND, GLOBAL SURVEYOR, Ionosphere, Longitude, VENUS
Abstract: International audience; In this paper we describe measurements of the Martian dayglow obtained by SPICAM UV spectrograph on board Mars Express between October 2004 and March 2005. Typical spectra (of more than 24,000 individual spectra) display the main features of the dayglow already reported more than 30 years ago (Barth et al., 1971, 1972). The variations with altitude, solar zenith angle, and aerocentric longitude of the main emissions, namely, the CO Cameron band emissions (a3Π – X1Σ+) from 180–260 nm, the CO2 + ultraviolet doublet (B2Σ+ - X2Π) emission near 289 nm, the O resonance line at 130.4 nm, and the H Lyman alpha line at 121.6 nm, are detailed. The average temperature deduced from the CO2 + (B2Σ+ - X2Π) emission scale height between 150 and 190 km is T∞ = 201 ± 10 K. The altitude of the peak of the dayglow emission varies from 120 km at low solar zenith angle (∼30°) up to 132 km at high solar zenith angle (∼75°). We also find 24 orbits in which the individual derived exospheric temperatures do not show significant variations with respect to solar zenith angle, aerocentric longitude, or longitude. The presence of crustal magnetic fields appears to correlate with a significant (∼100 K) increase in exospheric temperature. We report also the first observations of emissions associated with the N2 Vegard Kaplan band system in the Martian upper atmosphere.
Published: 2006
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174. Radar altimetery of Titan by the descending Huygens Probe

Author: Svedhem, V., Trautner, R., Falkner, P., Olivier Witasse, P Lebreton, J., Floury, N., Baptista, P., Wlodek Kofman, Alain Hérique, Lorenz, R., Dirk Plettemeier, Fulchignoni, M., Ferri, F., European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), 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), University of Arizona, Fakultaet fuer Elektrotechnik und Informationstechnik, Technische Universität Dresden = Dresden University of Technology (TU Dresden), Observatoire de Paris - Site de Meudon (OBSPM), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' (CISAS), and Universita degli Studi di Padova
Abstract: EGU05-A-10541; The Huygens probe carried a Radar altimeter as a part of its engineering system to determine the distance to the surface of Titan during the descent. Scientific data from this instrument was received and processed by the HASI instrument. During the descent the first surface signal was received at an altitude of 45km. This signal has been analysed to determine the topography and the scattering properties of the surface of Titan along the ground track traversed during the descent. The first results of this analysis will be presented and the limitations and the accuracy of the measurements will be discussed together with the geophysical implications.
Published: 2005

175. Prediction of a N2++layer in the upper atmosphere of Titan

Author: Odile Dutuit, Roland Thissen, Christian Alcaraz, Olivier Witasse, Jean Lilensten, Cyril Simon, Héloïse Soldi-Lose, Laboratoire de Chimie Physique D'Orsay (LCPO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-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), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), Laboratoire pour l'Utilisation du Rayonnement Electromagnétique (LURE) (LURE), and Centre Universitaire Paris-Sud
Subjects: Materials science, 010504 meteorology & atmospheric sciences, DOUBLE PHOTOIONIZATION, CHARGE-TRANSFER REACTIONS, IONIZATION FREQUENCIES, 01 natural sciences, Chemical reaction, CROSS-SECTIONS, Ion, Reaction rate, symbols.namesake, Metastability, 0103 physical sciences, EUV, Atmosphere of Titan, 010303 astronomy & astrophysics, Dissociative recombination, 0105 earth and related environmental sciences, IONOSPHERE, SOLAR CYCLE-21, STATE, Dication, MODEL, AERONOMIC CALCULATIONS, Geophysics, [SDU]Sciences of the Universe [physics], 13. Climate action, symbols, General Earth and Planetary Sciences, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Atomic physics, Titan (rocket family)
Abstract: International audience; Calculations of dication N2 ++ density in the atmosphere of Titan is performed for the first time. The metastable lifetime of this species is 3 seconds in its ground state. The density of the N2 ++ layer centred around 1100–1200 km altitude can reach 104 m−3. The ions are produced by both the double photoionisation and the photoelectron impact of N2. They are lost by dissociative recombination with the thermal electrons and chemical reactions with N2 and CH4. The most recent chemical reaction rate constants, given by laboratory experiments, were used in this study. Finally, we explore the possible detection of this ion layer by a spectrophotometer and show that the UVIS instrument onboard CASSINI could be capable to observe it.
Published: 2005
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176. Characterization of zonal winds in the stratosphere of Titan with UVES

Author: David Luz, A. Kaufer, Francesca Ferri, T. Civeit, L. M. Lara, Olivier Witasse, Daniel Gautier, Jean-Pierre Lebreton, Pascal Rannou, Regis Courtin, 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), Centro de Astronomia e Astrofísica da Universidade de Lisboa (CAAUL), Universidade de Lisboa = University of Lisbon (ULISBOA), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), 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), European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' (CISAS), Università degli Studi di Padova = University of Padua (Unipd), Universidade de Lisboa (ULISBOA), European Space Agency (ESA)-European Space Agency (ESA), and Universita degli Studi di Padova
Subjects: Physics, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Very Large Telescope, Solar System, 010504 meteorology & atmospheric sciences, Astronomy, Astronomy and Astrophysics, Scale height, 01 natural sciences, Atmosphère planétaire, symbols.namesake, Altitude, 13. Climate action, Space and Planetary Science, 0103 physical sciences, symbols, Titan (rocket family), Titan, 010303 astronomy & astrophysics, Doppler effect, Spectrograph, Stratosphere, 0105 earth and related environmental sciences
Abstract: Titan has been observed with UVES, the UV–Visual Echelle Spectrograph at the Very Large Telescope, with the aim of characterizing the zonal wind flow. We use a retrieval scheme originally developed for absolute stellar accelerometry [Connes, P., 1985. Astrophys. Space Sci., 110, 211–255] to extract the velocity signal by simultaneously taking into account all the lines present in the spectrum. The method allows to measure the Doppler shift induced at a given point by the zonal wind flow, with high precision. The short-wavelength channel (4200–5200 A) probes one scale height higher than the long-wavelength one (5200–6200 A), and we observe statistically significant evidence for stronger winds at higher altitudes. The results show a high dispersion. Globally, we detect prograde zonal winds, with lower limits of 62 and 50 m s−1 at the regions centered at 200 and 170 km altitude, but approximately a quarter of the measurements indicates null or retrograde winds.
Published: 2005
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177. A fast computation of the diurnal secondary ion production in the ionosphere of Titan

Author: Roland Thissen, Cyril Simon, Olivier Witasse, Odile Dutuit, Christian Alcaraz, Jean Lilensten, 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), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA), Laboratoire de Chimie Physique D'Orsay (LCPO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire pour l'utilisation du rayonnement électromagnétique (LURE), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-MENRT-Centre National de la Recherche Scientifique (CNRS), European Space Agency (ESA), Laboratoire pour l'Utilisation du Rayonnement Electromagnétique (LURE) (LURE), and Centre Universitaire Paris-Sud
Subjects: Physics, 010504 meteorology & atmospheric sciences, Computation, Analytic model, Astronomy and Astrophysics, Model parameters, Electron, Atmospheric sciences, 7. Clean energy, 01 natural sciences, Ion, symbols.namesake, Ionospheres, Space and Planetary Science, 0103 physical sciences, symbols, Solar radiation, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Ionosphere, Atomic physics, Titan (rocket family), Titan, 010303 astronomy & astrophysics, Electron ionization, 0105 earth and related environmental sciences
Abstract: International audience; We propose an analytic model that allows rapid computation of the secondary ion production due to electron impact from the primary photo-production in the ionosphere of Titan. The model parameters are given for each of the 5 major ion productions (N+2, CH+4, N+, CH+3, N++2) as well as for the electron production.
Published: 2005
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178. Discovery of an aurora on Mars

Author: Olivier Witasse, Oleg Korablev, Jean Lilensten, Bill R. Sandel, Eric Quémerais, Jean-Loup Bertaux, François Leblanc, S. A. Stern, 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), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), 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), Southwest Research Institute [Boulder] (SwRI), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Space Research Institute of the Russian Academy of Sciences (IKI), Russian Academy of Sciences [Moscow] (RAS), and Agence Spatiale Européenne = European Space Agency (ESA)
Subjects: Physics, Martian, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Solar System, Multidisciplinary, 010504 meteorology & atmospheric sciences, biology, Venus, Mars Exploration Program, Atmosphere of Mars, biology.organism_classification, 01 natural sciences, Astrobiology, L-shell, Atmosphere, 13. Climate action, Planet, 0103 physical sciences, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract: Aurorae have been observed on most planets in the Solar System. Mars seemed to be one of the exceptions — until Mars Express got there. Its SPICAM ultraviolet spectrometer has detected a martian aurora, different in important ways from any reported for other planets. The martian aurora is localized to one spot, clearly associated with the crustal magnetic field discovered and mapped by the Mars Global Surveyor. This field is a remnant of an ancient intrinsic magnetic field now extinct. In the high-latitude regions of Earth, aurorae are the often-spectacular visual manifestation of the interaction between electrically charged particles (electrons, protons or ions) with the neutral upper atmosphere, as they precipitate along magnetic field lines. More generally, auroral emissions in planetary atmospheres “are those that result from the impact of particles other than photoelectrons” (ref. 1). Auroral activity has been found on all four giant planets possessing a magnetic field (Jupiter2, Saturn3, Uranus4 and Neptune5), as well as on Venus, which has no magnetic field6. On the nightside of Venus, atomic O emissions at 130.4 nm and 135.6 nm appear in bright patches of varying sizes and intensities6, which are believed to be produced by electrons with energy
Published: 2005
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179. The OI 630.0 and 557.7nm dayglow measured by WINDII and modeled by TRANSCAR

Author: Olivier Witasse, F. Culot, Jean Lilensten, C. Lathuillere, 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), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), and EGU, Publication
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Solar zenith angle, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Kinetic energy, Atmospheric sciences, 01 natural sciences, 7. Clean energy, Latitude, Altitude, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, lcsh:QC801-809, Geology, Astronomy and Astrophysics, lcsh:QC1-999, Interferometry, lcsh:Geophysics. Cosmic physics, 13. Climate action, Space and Planetary Science, Physics::Space Physics, Orbit (dynamics), [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, lcsh:Q, Astrophysics::Earth and Planetary Astrophysics, Ionosphere, Thermosphere, lcsh:Physics
Abstract: A 1-D fluid/kinetic code is used to model WIND Imaging Interferometer measurements of the atomic oxygen (3P-1D) red and (-1D-1S) green thermospheric dayglows at 630.0nm and 557.7nm. This modelling is performed for different latitude and solar zenith angle conditions, in order to reproduce the measurements all along the satellite orbit. Results are successfully compared to the interferometer's observations, reproducing the measured volume emission rates, together with the maximum emission altitude. A good agreement is found regardless of the position considered along the satellite orbit, meaning that the solar flux and the solar zenith angle influences were successfully taken into account. Together with this model study, a four-year red and green oxygen lines set of WINDII data is analysed with regards to those geophysical parameters. Correlations between volume emission rates and solar flux are evaluated and it is found that the MgII index is better suited to this kind of study than the f10.7 decimetric index.
Published: 2004

180. Scientific objectives of the DYNAMO mission

Author: R. Lin, M. Moncuquet, François Leblanc, David L. Mitchell, C. Mazelle, John Clarke, L. Duvet, E. Lellouch, Tilman Spohn, D. Toublanc, J. Dyment, Michael E. Purucker, S. Smrekar, Robert M. Haberle, P. Tarits, R. Hodges, G. Balmino, J. Luhmann, Bruce M. Jakosky, Michel Parrot, François Forget, Y. Cohen, Eric Chassefière, J. Connerney, O. Grasset, A M Buckley, Paul Gough, Olivier Witasse, D. T. Young, D. Bass, J. Lilensten, Doris Breuer, M. Blanc, Eric Quémerais, Karoly Szego, Ph. Lognonné, G. Hulot, H. Rème, K. Issautier, Jean-Pierre Barriot, D. T. Lyons, Jean-Gabriel Trotignon, Stephen W. Bougher, N. Meyer, P.-L. Blelly, Michel Menvielle, K. Sperveslage, A. Nagy, Jean-Claude Cerisier, Jean-Loup Bertaux, F. Vial, D. Vignes, C. Berger, Gérard Chanteur, M. Pätzold, M. Parmentier, F. Hourdin, J.-A. Sauvaud, C. Sotin, M. Acuna, Sho Sasaki, G. M. Keating, J. L. Bougeret, Robert E. Johnson, H. Waite, F. Barlier, Jean-Jacques Berthelier, P. Pinet, P. Touboul, Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), 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), Centre d'étude spatiale des rayonnements (CESR), 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, Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-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), ONERA - The French Aerospace Lab [Palaiseau], ONERA-Université Paris Saclay (COmUE), 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), Institut de Physique du Globe de Paris (IPGP), Université Pierre et Marie Curie - Paris 6 (UPMC)-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), 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), Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), 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), 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), Observatoire de la Côte d'Azur (OCA), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne Occidentale - UFR Sciences et Techniques (UBO UFR ST), Université de Brest (UBO), Institut für Planetologie [Münster], Westfälische Wilhelms-Universität Münster (WWU), Institut für Geophysik und Meteorologie [Köln], Universität zu Köln, University of Sussex, Hungarian Academy of Sciences (MTA), The University of Tokyo (UTokyo), Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, NASA Goddard Space Flight Center (GSFC), Space Sciences Laboratory [Berkeley] (SSL), University of California [Berkeley], University of California-University of California, University of Virginia [Charlottesville], University of Michigan [Ann Arbor], University of Michigan System, University of Arizona, The George Washington University (GW), NASA Ames Research Center (ARC), University of Colorado [Boulder], University of Texas at Dallas [Richardson] (UT Dallas), Brown University, Southwest Research Institute [San Antonio] (SwRI), 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), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-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 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), 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), 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 national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Westfälische Wilhelms-Universität Münster = University of Münster (WWU), Universität zu Köln = University of Cologne, NASA-California Institute of Technology (CALTECH), University of California [Berkeley] (UC Berkeley), University of California (UC)-University of California (UC), and University of Virginia
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Aerospace Engineering, 01 natural sciences, Astrobiology, law.invention, Orbiter, law, 0103 physical sciences, Mercury's magnetic field, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, Atmospheric escape, Astronomy and Astrophysics, Mars Exploration Program, Aerobraking, Solar wind, Geophysics, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Physics::Space Physics, General Earth and Planetary Sciences, Timekeeping on Mars, Astrophysics::Earth and Planetary Astrophysics, Thermosphere
Abstract: International audience; DYNAMO is a small Mars orbiter planned to be launched in 2005 or 2007, in the frame of the NASA/ CNES Mars exploration program. It is aimed at improving gravity and magnetic field resolution, in order to better understand the magnetic, geologic and thermal history of Mars, and at characterizing current atmospheric escape, which is still poorly constrained. These objectives are achieved by using a low periapsis orbit, similar to the one used by the Mars Global Surveyor spacecraft during its aerobraking phases. The proposed periapsis altitude for DYNAMO of 120–130 km, coupled with the global distribution of periapses to be obtained during one Martian year of operation, through about 5000 low passes, will produce a magnetic/gravity field data set with approximately five times the spatial resolution of MGS. Additional data on the internal structure will be obtained by mapping the electric conductivity. Low periapsis provides a unique opportunity to investigate the chemical and dynamical properties of the deep ionosphere, thermosphere, and the interaction between the atmosphere and the solar wind, therefore atmospheric escape, which may have played a crucial role in removing atmosphere and water from the planet.
Published: 2001
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181. European Mars Science and Exploration Conference (EMSEC)

Author: Angelo Pio Rossi and Olivier Witasse
Subjects: Engineering, Space and Planetary Science, business.industry, Astronomy and Astrophysics, Mars Exploration Program, business, Astrobiology
Published: 2009
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182. Doubly-charged ions in the planetary ionospheres: a review

Author: Roland Thissen, Olivier Witasse, Cyril Simon Wedlund, Odile Dutuit, Guillaume Gronoff, and Jean Lilensten
Subjects: Physics, Solar System, biology, General Physics and Astronomy, Venus, Mars Exploration Program, biology.organism_classification, Ion, Astrobiology, Atmosphere, symbols.namesake, Planet, Physics::Space Physics, symbols, Terrestrial planet, Astrophysics::Earth and Planetary Astrophysics, Physical and Theoretical Chemistry, Titan (rocket family)
Abstract: This paper presents a review of the current knowledge on the doubly-charged atomic and molecular positive ions in the planetary atmospheres of the Solar System. It is focused on the terrestrial planets which have a dense atmosphere of N(2) or CO(2), i.e. Venus, the Earth and Mars, but also includes Titan, the largest satellite of Saturn, which has a dense atmosphere composed mainly of N(2) and a few percent of methane. Given the composition of these neutral atmospheres, the following species are considered: C(++), N(++), O(++), CH(4)(++), CO(++), N(2)(++), NO(++), O(2)(++), Ar(++) and CO(2)(++). We first discuss the status of their detection in the atmospheres of planets. Then, we provide a comprehensive review of their complex and original photochemistry, production and loss processes. Synthesis tables are provided for those ions, while a discussion on individual species is also provided. Methods for detecting doubly-charged ions in planetary atmospheres are presented, namely with mass-spectrometry, remote sensing and fine plasma density measurements. A section covers some original applications, like the possible effect of the presence of doubly-charged ions on the escape of an atmosphere, which is a key topic of ongoing planetary exploration, related to the evolution of a planet. The results of models, displayed in a comparative way for Venus, Earth, Mars and Titan, are discussed, as they can predict the presence of doubly-charged ions and will certainly trigger new investigations. Finally we give our view concerning next steps, challenges and needs for future studies, hoping that new scientific results will be achieved in the coming years and feed the necessary interdisciplinary exchanges amongst different scientific communities.
Published: 2011
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183. Planetary Upper Atmospheres, Ionospheres, and Magnetospheres

Author: Olivier Witasse
Subjects: Atmospheric Science, Geophysics, Space and Planetary Science, Aerospace Engineering, General Earth and Planetary Sciences, Environmental science, Astronomy and Astrophysics, Atmospheric sciences, Astrobiology
Published: 2005
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184. Prediction and modelling of doubly-charged ions in the earth's upper atmosphere

Author: Cyril Simon, Olivier Witasse, Odile Dutuit, Héloïse Soldi-Lose, Jean Lilensten, Christian Alcaraz, Roland Thissen, 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), Laboratoire de Chimie Physique D'Orsay (LCPO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Research and Scientific Support Department of ESA, European Space Agency (ESA), Laboratoire pour l'utilisation du rayonnement électromagnétique (LURE), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-MENRT-Centre National de la Recherche Scientifique (CNRS), and Agence Spatiale Européenne = European Space Agency (ESA)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Meteorology, Solar zenith angle, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Context (language use), 7. Clean energy, 01 natural sciences, Ion, Atmosphere, TheoryofComputation_ANALYSISOFALGORITHMSANDPROBLEMCOMPLEXITY, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, Electron ionization, Dissociative recombination, 0105 earth and related environmental sciences, Physics, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, lcsh:QC801-809, Geology, Astronomy and Astrophysics, lcsh:QC1-999, lcsh:Geophysics. Cosmic physics, Atmosphere of Earth, 13. Climate action, Space and Planetary Science, Physics::Space Physics, lcsh:Q, Astrophysics::Earth and Planetary Astrophysics, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Atomic physics, Ionosphere, lcsh:Physics
Abstract: International audience; We discuss the existence of the doubly-charged ions N2++, O2++ and O++ in the Earth's ionosphere through the theoretical computation of density profiles over the altitude range 100-500km calculated with the TRANSCAR model. Photoproductions and electron impact productions are described in detail. The photochemical equilibrium assumption verified in this context yields density profiles, validated by comparison to the measurements of the satellite Atmosphere Explorer. Those three dications are lost essentially by dissociative recombination and collisions with the neutrals N2, O2 and O. The metastable lifetime of N2++ is 3s and is estimated at 4s for O2++. A survey of the sensitivity to geophysical parameters (solar activity, latitude and solar zenith angle) is also shown. Emphasis is cast on the need for rate constants for chemical reactions involving doubly-charged ions. The fit of the model yields an estimated value of 1.06±0.40x10-10cm3s-1 for the rate constant of the O+++O reaction.

185. Prediction et modelisation des dications N2++, O2++ et O++ dans la haute atmosphere terrestre

Author: Cyril Simon, Jean Lilensten, Olivier Witasse, Roland Thissen, Odile Dutuit, Christian Alcaraz, Soldi-Lose, H., 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), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), Laboratoire de Chimie Physique D'Orsay (LCPO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire pour l'Utilisation du Rayonnement Electromagnétique (LURE) (LURE), Centre Universitaire Paris-Sud, Institut für Chemie, and Der Technischen Universität Berlin
Abstract: La presence d'ions doublement charges n'a jamais ete mise en evidence dans l'atmosphere terrestre. Suivant ce constat, nous presentons ici les premiers calculs theoriques complets de concentration pour les ions N2++, O2++ et O++. Le modele se decompose en deux etapes: nous calculons d'abord la photoionisation due aux photons EUV solaires, puis dans un deuxieme temps, nous resolvons l'equation de transport de Boltzmann pour les electrons suprathermiques grace au code d'ionisation TRANSCAR (Lilensten and Blelly, 2002). Les parametres photochimiques donnes en entree du code sont bases sur des mesures recentes en laboratoire (LCP/LURE). Nous calculons ensuite les productions primaires et secondaires entre 100 et 800 km d'altitude, tout en faisant une etude de sensibilite de la production electronique totale en periode solaire calme et active, a moyennes et hautes latitudes au dessus d'Eiscat. Les processus de perte chimique sont finalement inclus et moyennant l'hypothese verifiee de l'equilibre photochimique entre 100 et 500 km, nous pouvons predire les valeurs des concentrations de N2++, O2++ et O++. Enfin, dans une perspective plus large, l'accent est mis sur la partie validation des resultats et la fluorescence de ces trois dications, qui devrait permettre leur mise en evidence dans les spectres a haute resolution du ciel diurne.

186. The Huygens Probe Descent Trajectory Working Group: Organizational framework, goals, and implementation

Author: Miguel Pérez-Ayúcar, Dennis L. Matson, Olivier Witasse, David H. Atkinson, Jean-Pierre Lebreton, and Bobby Kazeminejad
Subjects: Scientific instrument, Organizational framework, Spacecraft, Computer science, business.industry, Astronomy and Astrophysics, Cassini/Huygens mission, law.invention, symbols.namesake, Orbiter, Space and Planetary Science, law, Entry and descent trajectory reconstruction, symbols, Titan (rocket family), business, Remote sensing
Abstract: Cassini/Huygens, a flagship mission to explore the rings, atmosphere, magnetic field, and moons that make up the Saturn system, is a joint endeavor of the National Aeronautics and Space Administration, the European Space Agency, and Agenzia Spaziale Italiana. Comprising two spacecraft - a Saturn orbiter built by NASA and a Titan entry/descent probe built by the European Space Agency, Cassini/Huygens was launched in October 1997. The Huygens probe parachuted to the surface of Titan in January 2005. During the descent, six science instruments provided in situ measurements of Titan’s atmosphere, clouds, and winds, and photographed Titan’s surface. To correctly interpret and correlate results from the probe science experiments, and to provide a reference set of data for ground-truth calibration of orbiter remote sensing measurements, an accurate reconstruction of the probe entry and descent trajectory and surface landing location is necessary. The Huygens Descent Trajectory Working Group was chartered in 1996 as a subgroup of the Huygens Science Working Team to develop and implement an organizational framework and retrieval methodologies for the probe descent trajectory reconstruction from the entry altitude of 1270 km to the surface using navigation data, and engineering and science data acquired by the instruments on the Huygens Probe. This paper presents an overview of the Descent Trajectory Working Group, including the history, rationale, goals and objectives, organizational framework, rules and procedures, and implementation.
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187. Multi-Instrument Observations of an Aurora-Type Event by Mars Express

Author: François Leblanc, Olivier Witasse, Jean Lilensten, Frahm, R. A., Ali Safaeinili, Brain, D., Jeremie Mouginot, Jean-Loup Bertaux, Wlodek Kofman, Lundin, R., Halekas, Jasper S., Holmström, M., 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), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), 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), Space Science and Engineering Division [San Antonio], Southwest Research Institute [San Antonio] (SwRI), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Space Sciences Laboratory [Berkeley] (SSL), University of California [Berkeley], University of California-University of California, Swedish Institute of Space Physics [Uppsala] (IRF), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), University of California [Berkeley] (UC Berkeley), and University of California (UC)-University of California (UC)
Subjects: [SDU]Sciences of the Universe [physics]
Abstract: International audience; We present a new set of observations of Martian aurora obtained by SPICAM UV spectrometer on board Mars Express (MEX). Several auroral emissions are identified on the Martian night side near crustal magnetic fields. During several orbits consecutive events separated by several tens of seconds are observed, highlighting the role of closed and open field line structures in shaping spatially these events. For most of these events coordinated observations with MARSIS and ASPERA-3 on board Mars Express were possible. ASPERA-3 is composed of an ion mass analyzer (IMA), of two neutral particle imager (NPI and NPD) and of one electron spectrometer (ELS). For these particular events, data from the electron spectrometer were available so that a simultaneous measurement of the precipitating electron flux was possible. MARSIS is a multifrequency synthetic aperture orbital sounding radar which monitors in particular the Total Electron Content (TEC) and which was operating for some of these events. At the end, SPICAM UVS is a UV spectrograph covering the spectral range between 110 and 300 nm and which measures the atmospheric glow. It is this latter instrument which clearly provides the spectral evidence of the occurrence of an auroral-event. In order to avoid any ambiguity on the positions of the simultaneous measurements, we used orbits of MEX during which SPICAM UVS field of view was nadir oriented. This new set of observations shows quite strong coincidences between the occurrence of energetic precipitating electrons into the Martian atmosphere, the increase of the TEC, the presence of crustal magnetic field anomalies and auroral-type glow. Following the definition of Brain et al. (2007) of open / closed magnetic field lines, we observe that the aurora detected by SPICAM UVS occur on open field lines. This conclusion therefore suggests a significant relation between aurora events at Mars and the presence of cusp like magnetic field line structures.

188. Dications in the planetary ionospheres

Author: Jean Lilensten, Olivier Witasse, Cyril Simon, Guillaume Gronoff, Roland Thissen, Odile Dutuit, Christian Alcaraz, Soldi-Lose, H., Francheschi, P., Jan Zabka, Avakian, S. V., 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), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), Laboratoire de Chimie Physique D'Orsay (LCPO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut für Chemie, Der Technischen Universität Berlin, Laboratorio di Fisica Atomica e Molecolare, J. Heyrovský Institute of Physical Chemistry, J. Heyrovsky Institute of Physical Chemistry, and All-Russia Scientific center
Subjects: Physics::Plasma Physics, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics
Abstract: The planetary ionosphere models usually consider singly charged ions only and neglect doubly charged ions and especially the molecular ones since they were thought to be unstable in ionospheric conditions. Generally speaking, doubly charged ions are difficult to detect by mass spectrometry because their q/m number is the same as other more abundant ions. Therefore, only 0++ have already been identified in Earth and Venus' atmospheres. Due to recent and dedicated laboratory experiments on reaction rates and cross sections, specific models of doubly charged ions -atomic and molecular- have been developed for the Earth, Mars, Titan and Venus. In this communication, we shall: - explain why these ions are of interest; - review which ions have been detected, and where; - review the relevant ion-neutral photo-chemistry, the laboratory measurements, and the current models.

189. Radiative trail of the PHOENIX entry

Author: Olivier Witasse, M. Lino da Silva, and R. Sobbia
Subjects: Physics, biology, Radiative transfer, Phoenix, biology.organism_classification, Atmospheric sciences

190. Magnetic Structure and Propagation of Two Interacting CMEs From the Sun to Saturn

Author: T. J. Bradley, Teresa Nieves-Chinchilla, Yoshifumi Futaana, Emilia Kilpua, Adam Masters, Erika Palmerio, Lan Jian, Beatriz Sánchez-Cano, Elias Roussos, Laurent Lamy, David G. Barnes, M. Leila Mays, Christian Möstl, G. Provan, Olivier Witasse, Andrei Zhukov, Chihiro Tao, The Royal Society, University of California [Berkeley], University of California, NASA Goddard Space Flight Center (GSFC), University of Helsinki, STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Royal Observatory of Belgium [Brussels] (ROB), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), School of Physics and Astronomy [Leicester], University of Leicester, National Institute of Information and Communications Technology [Tokyo, Japan] (NICT), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Austrian Academy of Sciences (OeAW), Graz University of Technology [Graz] (TU Graz), Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Swedish Institute of Space Physics [Kiruna] (IRF), The Blackett Laboratory, Department of Physics, Space Physics Research Group, University of California [Berkeley] (UC Berkeley), University of California (UC), Helsingin yliopisto = Helsingfors universitet = University of Helsinki, Agence Spatiale Européenne = European Space Agency (ESA), Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Blackett Laboratory, and Imperial College London
Subjects: heliophysics, 010504 meteorology & atmospheric sciences, INTERACTION REGIONS, FOS: Physical sciences, Venus, interplanetary magnetic field, 114 Physical sciences, 01 natural sciences, KILOMETRIC RADIATION, Heliophysics, Physics - Space Physics, FORBUSH DECREASES, Saturn, COSMIC-RAY INTENSITY, 0103 physical sciences, 0201 Astronomical and Space Sciences, STREAM INTERACTIONS, Coronal mass ejection, Astrophysics::Solar and Stellar Astrophysics, COMPLEX EJECTA, Interplanetary magnetic field, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), coronal mass ejections, 0105 earth and related environmental sciences, Earth and Planetary Astrophysics (astro-ph.EP), Physics, biology, heliosphere, Astronomy, biology.organism_classification, Space Physics (physics.space-ph), WHITE-LIGHT, Solar wind, Geophysics, Astrophysics - Solar and Stellar Astrophysics, solar wind, HIGH-LATITUDES, 13. Climate action, Space and Planetary Science, SOLAR ENERGETIC PARTICLES, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, 0401 Atmospheric Sciences, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Interplanetary spaceflight, Heliosphere, Astrophysics - Earth and Planetary Astrophysics
Abstract: One of the grand challenges in heliophysics is the characterisation of coronal mass ejection (CME) magnetic structure and evolution from eruption at the Sun through heliospheric propagation. At present, the main difficulties are related to the lack of direct measurements of the coronal magnetic fields and the lack of 3D in-situ measurements of the CME body in interplanetary space. Nevertheless, the evolution of a CME magnetic structure can be followed using a combination of multi-point remote-sensing observations and multi-spacecraft in-situ measurements as well as modelling. Accordingly, we present in this work the analysis of two CMEs that erupted from the Sun on 28 April 2012. We follow their eruption and early evolution using remote-sensing data, finding indications of CME--CME interaction, and then analyse their interplanetary counterpart(s) using in-situ measurements at Venus, Earth, and Saturn. We observe a seemingly single flux rope at all locations, but find possible signatures of interaction at Earth, where high-cadence plasma data are available. Reconstructions of the in-situ flux ropes provide almost identical results at Venus and Earth but show greater discrepancies at Saturn, suggesting that the CME was highly distorted and/or that further interaction with nearby solar wind structures took place before 10 AU. This work highlights the difficulties in connecting structures from the Sun to the outer heliosphere and demonstrates the importance of multi-spacecraft studies to achieve a deeper understanding of the magnetic configuration of CMEs., Comment: 40 pages, 11 figures, accepted for publication in Journal of Geophysical Research: Space Physics
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191. Modelling N2++, O2++, O++ in planetary ionospheres

Author: Cyril Simon, Jean Lilensten, Olivier Witasse, Odile Dutuit, Roland Thissen, Christian Alcaraz, Soldi-Lose, H., 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), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), Laboratoire de Chimie Physique D'Orsay (LCPO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire pour l'Utilisation du Rayonnement Electromagnétique (LURE) (LURE), and Centre Universitaire Paris-Sud

192. L'instrument Micro-ARES sur ExoMars 2016

Author: Déprez, Grégoire, 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), Université Pierre et Marie Curie - Paris VI, Franck Montmessin, Olivier Witasse, and STAR, ABES
Subjects: Sonde de potentiel, Atmospheric electricity, Électricité atmosphérique, Plasma collisionnel, Mars, Dust, Poussière, [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ExoMars
Abstract: Atmosphere ionization and electrification mechanisms of various sorts are known to exist in most of the planetary environments. It appears that the lower atmosphere and surface of Mars combine a number of favorable conditions for the development of intense atmospheric electric fields. Unveiling the Martian atmospheric electricity was the original goal of Micro-ARES, the electric-field and conductivity sensor of the DREAMS meteorological suite, the only scientific payload that equipped the Schiaparelli module from the ExoMars 2016 mission.The study of the electrical activity and electric field generation in Martian dust events might bring new capital knowledge on a wide range of phenomena: The local and planetary scale dust dynamics, a major component of the Martian climate, the partially understood Martian ionosphere, atmospheric chemistry and more precisely the production and destruction of the Martian methane, a still unresolved mystery.The following thesis details the hardware and software development of Micro-ARES, its testing phases, both in laboratory and on the field, and the data processing and physical processes underlying the instrument’s operation. Since future missions may carry again these kind of polyvalent, lightweight and energy-efficient sensor, emphasis was put on the modeling of the instrument's electrical coupling with the atmosphere. This theoretical work exceeds the frame of Micro-ARES in ExoMars 2016 and is necessary in order to understand and accurately compensate the biases induced by the instrument's surroundings, its simplified design and the unexpected electrical behavior of the Martian atmosphere., Divers phénomènes d'ionisation et d'électrification atmosphériques existent dans la plupart des environnements planétaires connus et les conditions dans la basse atmosphère de Mars sont propices à l'établissement de champs électriques potentiellement très élevés. La raison d'être de Micro-ARES, le capteur de champ électrique et de conductivité de la suite météo DREAMS, seule charge utile scientifiques de l'atterrisseur Schiaparelli de la mission ExoMars 2016, était de défricher cette électricité atmosphérique martienne. L’étude de l’activité électrique ainsi que de la génération de ces champs électriques dans les tempêtes de poussières martiennes permettrait de faire la lumière sur divers phénomènes physiques : La dynamique des poussières à l’échelle locale et planétaire, élément clé du climat martien, la peu comprise ionosphère martienne ou encore la chimie atmosphérique et plus précisément l’énigme du méthane martien.La thèse présentée ici détaille le développement matériel et logiciel de Micro-ARES, les tests subits par l’instrument aussi bien en chambre que sur le terrain, ainsi que le traitement des données et la physique qui sous-tend le fonctionnement de l’instrument. Puisque de futures mission embarqueront très probablement ce type de capteur polyvalent, léger et consommant peu, l’accent a été mis sur la modélisation de l’interaction entre l’électrode et l’atmosphère. Ce travail théorique dépasse le cadre de Micro-ARES sur ExoMars 2016 et est une étape nécessaire dans la compréhension et le traitement des biais induits aussi bien par l’environnement de l’instrument, son design simplifié et les comportements inattendus de l’atmosphère martienne.
Published: 2017

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