9 results on '"Dehant, V"'
Search Results
2. Expected performance of the NetLander geodesy experiment
- Author
-
Folkner, W. M, Yoder, C. F, Preston, R. A, Wu, S. C, Romans, L. J, Barriot, J. -P, and Dehant, V
- Subjects
Geophysics - Published
- 2001
3. Monitoring Global Geophysical Fluids by Space Geodesy
- Author
-
Chao, Benjamin F, Dehant, V, Gross, R. S, Ray, R. D, Salstein, D. A, and Watkins, M
- Subjects
Geophysics - Abstract
Since its establishment on 1/1/1998 by the International Earth Rotation Service, the Coordinating Center for Monitoring Global Geophysical Fluids (MGGF) and its seven Special Bureaus have engaged in an effort to support and facilitate the understanding of the geophysical fluids in global geodynamics research. Mass transports in the atmosphere-hydrosphere-solid Earth-core system (the "global geophysical fluids") will cause the following geodynamic effects on a broad time scale: (1) variations in the solid Earth's rotation (in length-of-day and polar motion/nutation) via the conservation of angular momentum and effected by torques at the fluid-solid Earth interface; (2) changes in the global gravitational field according to Newton's gravitational law; and (3) motion in the center of mass of the solid Earth relative to that of the whole Earth ("geocenter") via the conservation of linear momentum. These minute signals have become observable by space geodetic techniques, primarily VLBI, SLR, GPS, and DORIS, with ever increasing precision/accuracy and temporal/spatial resolution. Each of the seven Special Bureaus within MGGF is responsible for calculations related to a specific Earth component or aspect -- Atmosphere, Ocean, Hydrology, Ocean Tides, Mantle, Core, and Gravity/Geocenter. Angular momenta and torques, gravitational coefficients, and geocenter shift will be computed for geophysical fluids based on global observational data, and from state-of-the-art models, some of which assimilate such data. The computed quantities, algorithm and data formats are standardized. The results are archived and made available to the scientific research community. This paper reports the status of the MGGF activities and current results.
- Published
- 1999
4. Monitoring Global Geophysical Fluids with Respect to Large-Scale Geodynamic Properties
- Author
-
Chao, B, Dehant, V, Gross, R, Ray, R, Salstein, D, and Watkins, M
- Subjects
Geophysics - Published
- 1999
5. Internal loading of an inhomogeneous compressible Earth with phase boundaries
- Author
-
Defraigne, P, Dehant, V, and Wahr, J. M
- Subjects
Geophysics - Abstract
The geoid and the boundary topography caused by mass loads inside the earth were estimated. It is shown that the estimates are affected by compressibility, by a radially varying density distribution, and by the presence of phase boundaries with density discontinuities. The geoid predicted in the chemical boundary case is 30 to 40 percent smaller than that predicted in the phase case. The effects of compressibility and radially varying density are likely to be small. The inner core-outer core topography for loading inside the mantle and for loading inside the inner core were computed.
- Published
- 1996
6. Influence of triaxiality and second-order terms in flattenings on the rotation of terrestrial planets: I. Formalism and rotational normal modes
- Author
-
Van Hoolst, T. and Dehant, V.
- Subjects
- *
PLANETS , *GEOPHYSICS - Abstract
Unlike for the Earth, the equatorial flattening of Mars is important and almost of the same magnitude as the polar flattening. The classical semi-analytical model for the rotation of an ellipsoidal rotating planet with an elastic mantle and incompressible fluid core is therefore extended to incorporate the effects of the planet’s triaxiality. As triaxiality effects are nevertheless small, other second-order effects in the small parameters not related to triaxiality have also been taken into account. The absolute values of the frequencies of two rotational normal modes: (1) the free core nutation (FCN); and (2) the Chandler wobble (CW), are found to be smaller than the corresponding frequencies for a biaxial planet. The period change is larger for the CW than for the FCN, for which the triaxiality effect is comparable to the effect associated with the other second-order terms, and amounts to about 1 day for the CW of Mars. [Copyright &y& Elsevier]
- Published
- 2002
- Full Text
- View/download PDF
7. Long Lived Martian Geoscience Observatory
- Author
-
Philippe Lognonné, Spohn, T., Breuer, D., Christensen, U., Igel, H., Dehant, V., Hoolst, T., Giardini, D., Primdahl, F., Merayo, J., Vennerstroem, S., Garcia, R., Mark Wieczorek, Sotin, C., Mocquet, A., Langlais, B., Jean-Jacques Berthelier, Michel Menvielle, Pais, A., Pike, W. T., Szarka, L., Den Berg, A., 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), F. Favata, J. Sanz-Forcada, A. Giménez, and B. Battrick, Cardon, Catherine, F. Favata, J. Sanz-Forcada, A. Giménez, and B. Battrick, Institut de Physique du Globe de Paris, DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Gesellschaft, Department of Earth and Environmental Sciences [München], Ludwig-Maximilians-Universität München (LMU), Royal Observatory of Belgium [Brussels] (ROB), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Technical University of Denmark [Lyngby] (DTU), Danish Space Research Institute (DSRI), 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), Department of Physics [Coimbra], University of Coimbra [Portugal] (UC), Imperial College London, Geodetic and Geophysical Research Institute (GGRI), Research Centre for Astronomy and Earth Sciences [Budapest], Hungarian Academy of Sciences (MTA)-Hungarian Academy of Sciences (MTA), Utrecht University [Utrecht], and and B. Battrick (eds.)
- Subjects
Geophysics ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,[SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] ,[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph] ,[PHYS.PHYS.PHYS-PLASM-PH] Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph] ,Habitability ,Astrogeology ,[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP] ,Atmospheric science ,Planets ,Mars ,Moon ,[SDU.ASTR] Sciences of the Universe [physics]/Astrophysics [astro-ph] - Abstract
International audience; If the apparition of life is maybe a rapid process on a habitable planet, the evolution of life toward intelligence is a much longer process and about 4000 Myears were needed on the Earth. What is the probability for a telluric planet to offer the right conditions to life evolution? Why is the Earth the only planet on the Solar System where liquid water was able to be maintained liquid at the surface, and why Mars and Venus were unable to maintain such temperature conditions? What is the level of volcanic ac- tivity on Mars? What is the heat flow and its impact on the temperature gradient in the subsurface? How can we extrapolate this activity in the past and estimate the im- portance of volcanic degazing and its impact on the early atmosphere?Do we have indications for an early plate tectonics regime on Mars with a water rich upper mantle and how im- portant is such a regime in the habitability of planets? Why and when stopped the Martian dynamo? All these scientific questions, which impact on the Martian long term habitability, are related to the geodynamics of the planet and its geological evolution and activity. In order to provide an answer, we need to understand how a tel- luric planet is geologically evolving, which needs a detailed knowledge of its interior structure, of the mineralogy and temperature of its mantle, of the amount of energy re- leased during accretion and therefore of the size of the main units of the planet (crust, mantle, core), of the heat flux and possibly of the long scale convective structure. We also need to monitor its present geological activity. The Long Lived Geoscience Observatory on Mars will setup a permanent network of fixed stations on the planet, op-erating for a decade or more. These stations will moni- tor with high resolution the magnetic field, the rotation and the seismic activity of the planets, will measure the heat flux and will in addition monitor the present envi- ronment (meteorology, radiations, ionospheric properties, etc) and support human exploration. This suite of instru- ment will be able to perform a passive sounding of the deep and shallow planetary interior and to retrieve the temperature profile and mineralogical profile in the planet and 3D mantle lateral variation by a joint inversion of the seismic, conductivity profiles and heat flux and geodetic data. 8 stations, operating for 4 to 10 years will be nec- essary to obtain such detailed tomographic picture of the mantle convection and we can therefore expect a full de- ployment after 4 or 5 Mars windows. Such stations, com- parable to the of Autonomous Lunar Surface Experiment Package, deployed by NASA during the Apollo missions, might be deployed systematically by all the future Mars landing missions and might therefore be an original Euro- pean contribution to the International Mars exploration in the next decade and will complement with the necessary geophysical data the analysis of the future sample return missions. In addition to Roving and Sample Return mis- sion, they also can be deployed by more dedicated multi- lander missions. In addition, such stations might also be proposed to the future Moon landing missions. In both cases, these Planetary Long Lived Observatories will not only help us to better understand the formation and evo- lution of two of the Solar Systems Terrestrial Planets, but will also support human exploration by a permanent sur- vey of the planetary environment.
8. InSight - The First Three Months on Mars
- Author
-
Banerdt, B., Smrekar, S., Antonangeli, D., Asmar, Sami, Bandfield, J.L., Beghein, C., Bowles, Neil, Bozdag, E., Chi, P. J., Christensen, U., Clinton, John, Collins, G., Daubar, I., Dehant, V., Fillingim, M., Folkner, W., Garcia, R., Garvin, J., Giardini, D., Golombek, M., Grant, J.A., Grott, Matthias, Müller, Nils, Plesa, Ana-Catalina, and Spohn, Tilman
- Subjects
Geophysics ,Planetenphysik ,HP3 ,Leitungsbereich PF ,Mars ,InSight
9. Penetrators for in situ subsurface investigations of Europa
- Author
-
Gowen, R.A., Smith, A., Fortes, A.D., Barber, S., Brown, P., Church, P., Collinson, G., Coates, A.J., Collins, G., Crawford, I.A., Dehant, V., Chela-Flores, J., Griffiths, A.D., Grindrod, P.M., Gurvits, L.I., Hagermann, A., Hussmann, H., Jaumann, R., Jones, A.P., and Joy, K.H.
- Subjects
- *
GEOPHYSICS , *SPACE biology , *COST effectiveness , *EXPLORATION of Jupiter , *OBSERVATIONS of Jupiter , *EUROPA (Satellite) , *JUPITER (Planet) ,SURFACE of Europa - Abstract
Abstract: We present the scientific case for inclusion of penetrators into the Europan surface, and the candidate instruments which could significantly enhance the scientific return of the joint ESA/NASA Europa-Jupiter System Mission (EJSM). Moreover, a surface element would provide an exciting and inspirational mission highlight which would encourage public and political support for the mission. Whilst many of the EJSM science goals can be achieved from the proposed orbital platform, only surface elements can provide key exploration capabilities including direct chemical sampling and associated astrobiological material detection, and sensitive habitability determination. A targeted landing site of upwelled material could provide access to potential biological material originating from deep beneath the ice. Penetrators can also enable more capable geophysical investigations of Europa (and Ganymede) interior body structures, mineralogy, mechanical, magnetic, electrical and thermal properties. They would provide ground truth, not just for the orbital observations of Europa, but could also improve confidence of interpretation of observations of the other Jovian moons. Additionally, penetrators on both Europa and Ganymede, would allow valuable comparison of these worlds, and gather significant information relevant to future landed missions. The advocated low mass penetrators also offer a comparatively low cost method of achieving these important science goals. A payload of two penetrators is proposed to provide redundancy, and improve scientific return, including enhanced networked seismometer performance and diversity of sampled regions. We also describe the associated candidate instruments, penetrator system architecture, and technical challenges for such penetrators, and include their current status and future development plans. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.