J. Brillet

Publications (32)24.95 Total impact

• Article: A cometary origin for CO in the stratosphere of Saturn?

  T. Cavalié, P. Hartogh, F. Billebaud, M. Dobrijevic, T. Fouchet, E. Lellouch, T. Encrenaz, J. Brillet, G. H. Moriarty-Schieven
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  ABSTRACT: Context. The CO(3–2) line has been observed in the atmosphere of Saturn. The CO(3–2) observation proves that an external source of CO exists in the stratosphere of the planet. Aims. We attempt to constrain the type and magnitude of the external source of CO in the atmosphere of Saturn, by observing the emission core of the CO(6–5) line. Methods. We observed the CO(6–5) line at the limbs of Saturn. We analysed the observations by means of a 1-D transport model of the atmosphere of Saturn, coupled with a radiative transfer model. Results. We obtained a high signal-to-noise ratio spectrum that confirms the existence of an external source of CO in the stratosphere of Saturn.We demonstrated that a cometary origin of CO is the most probable, an impact occurring 220±30 years ago and depositing (2.1 ± 0.4) × 1015 g of CO above 0.1 mbar. However, we cannot totally reject the possibility of CO originating (at least partially) in a steady source. Conclusions. Complete photochemical modelling of the oxygen compounds is required to determine realistic error bars of the inferred quantities and to conclude on the origin of CO.
  Astronomy and Astrophysics 01/2010; 510:A88. · 4.59 Impact Factor
• Article: First observation of CO at 345GHz in the atmosphere of Saturn with the JCMT: New constraints on its origin

  T. Cavalié, F. Billebaud, M. Dobrijevic, T. Fouchet, E. Lellouch, T. Encrenaz, J. Brillet, G.H. Moriarty-Schieven, J.G.A. Wouterloot, P. Hartogh
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  ABSTRACT: We have performed the first observation of the CO(3-2) spectral line in the atmosphere of Saturn with the James Clerk Maxwell Telescope. We have used a transport model of the atmosphere of Saturn to constrain the origin of the observed CO. The CO line is best-fit when the CO is located at pressures less than (15±2) mbar with a mixing ratio of (2.5±0.6)×10-8 implying an external origin. By modeling the transport in Saturn’s atmosphere, we find that a cometary impact origin with an impact 200–350 years ago is more likely than continuous deposition by interplanetary dust particles (IDP) or local sources (rings/satellites). This result would confirm that comet impacts are relatively frequent and efficient providers of CO to the atmospheres of the outer planets. However, a diffuse and/or local source cannot be rejected, because we did not account for photochemistry of oxygen compounds. Finally, we have derived an upper limit of ∼1×10-9 on the tropospheric CO mixing ratio.
  Icarus 01/2009; 203(2):531-540. · 3.38 Impact Factor
• Conference Proceeding: CO in the atmospheres of Saturn and Uranus. Observations at millimeter and submillimeter wavelengths.

  T Cavalié, F Billebaud, M Dobrijevic, T Fouchet, E Lellouch, J Brillet, T Encrenaz, G ~H Moriarty-Schieven, J Wouterloot
  SF2A-2008; 11/2008
• Conference Proceeding: CO in the Atmosphere of Saturn. Observations at Millimeter and Submillimeter Wavelengths

  T Cavalié, F Billebaud, M Dobrijevic, T Fouchet, E Lellouch, J Brillet, T Encrenaz, G Moriarty-Schieven, J Wouterloot
  AAS/Division for Planetary Sciences Meeting Abstracts #40; 09/2008
• Article: Odin space telescope monitoring of water vapor in the stratosphere of Jupiter

  T Cavalié, N Biver, P Hartogh, M Dobrijevic, F Billebaud, E Lellouch, Aa Sandqvist, J Brillet, A Lecacheux, A Hjalmarson, U Frisk, M Olberg, The Odin Team
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  ABSTRACT: a b s t r a c t The Odin space telescope has monitored the H 2 O (1 10 –1 01) line in Jupiter's stratosphere over the 2003–2009 period. When comparing these data with previous spectra obtained with SWAS and Odin over the 1999–2002 period, we see no significant variations in the line-to-continuum ratio of the H 2 O line over the whole period. We have however tentatively identified a decrease by $ 15% of the line-to-continuum ratio between 2002 and 2007–2009, indicating that there was less H 2 O in the stratosphere of Jupiter in 2007–2009 than anticipated. We have tested the IDP (interplanetary dust particles) and SL9 (Shoemaker-Levy 9) 1D time-dependent models presented in Cavalié et al. [2008, Observation of water vapor in the stratosphere 613 of Jupiter with the Odin space telescope. Planetary and Space Science 56, 1573–1584]. We present a series of scenarios that lead to satisfactory fits of the whole data set (1999–2002 and 2003–2009 periods) based on IDP and SL9 models. The evolution of Jupiter's stratospheric H 2 O that we have tentatively observed has however to be confirmed by Herschel/HIFI observations. If the decrease of the line-to-continuum ratio is confirmed by future observations, it would be a direct evidence that Jupiter's H 2 O comes from SL9. In addition, this study shows that new constraints on Jupiter's eddy diffusion coefficient profile could be obtained (in the pressure ranges that are probed) from the monitoring of SL9 species in its stratosphere.
  Planetary and Space Science 05/2008; 56:1573-1584. · 2.22 Impact Factor
• Article: CO IN THE ATMOSPHERES OF SATURN AND URANUS. OBSERVATIONS AT MILLIMETER AND SUBMILLIMETER WAVELENGTHS

  T Cavalié, F Billebaud, M Dobrijevic, T Fouchet, E Lellouch, J Brillet, T Encrenaz
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  ABSTRACT: An external supply of oxygenated compounds exists in outer planets. Carbon monoxide has been detected in each giant planet. The source of CO has been proved to be dual (internal and external) in Jupiter and Neptune, but this is still unclear in the case of Saturn and Uranus. Therefore, constraining the amount of CO in the troposphere and stratosphere of these planets would help solve this problem. We performed observations of Saturn and Uranus at millimeter and submillimeter wavelengths in the CO (1-0), (2-1) and (3-2) lines. Observations were carried out with the IRAM 30-m telescope (Pico Veletta, Spain) in September 2006 and with the JCMT 15-m telescope (Hawaii, USA) in January 2008. We have recorded broad multi-band spectra of each planet. The results of these observations are presented and discussed.
  SF2A. 01/2008;
• Source

  Available from: Michel Dobrijevic

  Article: Vertical temperature profile and mesospheric winds retrieval on Mars from CO millimeter observations. Comparison with general circulation model predictions

  T. Cavalié, F. Billebaud, T. Encrenaz, M. Dobrijevic, J. Brillet, F. Forget, E. Lellouch
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  ABSTRACT: We have compared observations of the planetary mean thermal profile and mesospheric wind velocities on the disk, obtained with our millimetric observations of CO rotational lines, to predictions from the Laboratoire de M´et´eorologie Dynamique (LMD) Mars General Circulation Model, as provided through the Mars Climate Database (MCD) numerical tool. Methods. We observed the atmosphere of Mars at CO(1-0) and CO(2-1) wavelengths with the IRAM 30-m antenna in June 2001 and November 2005. We retrieved the mean thermal profile of the planet from high and low spectral resolution data with an inversion method detailed here. High spectral resolution spectra were used to derive mesospheric wind velocities on the planetary disk. We also report here the use of 13CO(2-1) line core shifts to measure wind velocities at 40 km. Results. Neither theMars Year 24 (MY24) nor the Dust Storm scenario from theMars Climate Database (MCD) provides satisfactory fits to the 2001 and 2005 data when retrieving the thermal profiles. The Warm scenario only provides good fits for altitudes lower than 30 km. The atmosphere is warmer than predicted up to 60 km and then becomes colder. Dust loading could be the reason for this mismatch. The MCD MY24 scenario predicts a thermal inversion layer between 40 and 60 km, which is not retrieved from the high spectral resolution data. Our results are generally in agreement with other observations from 10 to 40 km in altitude, but our results obtained from the high spectral resolution spectra differ in the 40-70 km layer, where the instruments are the most sensitive. The wind velocities we retrieve from our 12CO observations confirm MCD predictions for 2001 and 2005. Velocities obtained from 13CO observations are consistent with MCD predictions in 2001, but are lower than predicted in 2005.
  Astronomy and Astrophysics 01/2008; 489:795–809. · 4.59 Impact Factor
• Article: Observation of water vapor in the stratosphere of Jupiter with the Odin space telescope

  T. Cavalié, F. Billebaud, N. Biver, M. Dobrijevic, E. Lellouch, J. Brillet, A. Lecacheux, Å. Hjalmarson, Aa. Sandqvist, U. Frisk, M. Olberg, E.A. Bergin
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  ABSTRACT: The water vapor line at 557 GHz has been observed with the Odin space telescope with a high signal-to-noise ratio and a high spectral resolution on November 8, 2002. The analysis of this observation as well as a re-analysis of previously published observations obtained with the submillimeter wavelength astronomy satellite seem to favor a cometary origin (Shoemaker-Levy 9) for water in the stratosphere of Jupiter, in agreement with the ISO observation results. Our model predicts that the water line should become fainter and broader from 2007. The observation of such a temporal variability would be contradictory with an IDP steady flux, thus supporting the SL9 source hypothesis.
  Planetary and Space Science 01/2008; 56(12):1573-1584. · 2.22 Impact Factor
• Conference Proceeding: The Origin of Water Vapor in the Stratosphere of Jupiter: SWAS and Odin Observations

  T Cavalié, F Billebaud, E Lellouch, N Biver, M Dobrijevic, J Brillet, A Lecacheux, A Hjalmarson, A Sandqvist, U Frisk, M Olberg, Odin Team, E ~A Bergin
  AAS/Division for Planetary Sciences Meeting Abstracts #39; 10/2007
• Article: The Origin of Water Vapor in the Stratosphere of Jupiter: SWAS and Odin Observations

  Thibault Cavalié, F. Billebaud, E. Lellouch, N. Biver, M. Dobrijevic, J. Brillet, A. Lecacheux, A. Hjalmarson, A. Sandqvist, U. Frisk, M. Olberg, Odin Team, E. A. Bergin
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  ABSTRACT: The Infrared Space Observatory (ISO) has detected water vapor in the stratospheres of the giant planets and Titan and CO2 on Jupiter, Saturn and Neptune (Feuchtgruber et al. 1997, 1999, Lellouch et al. 1997). The presence of the atmospheric cold trap implies an external origin for H2O (interplanetary dust (IDP), sputtering from the satellites and /or rings, large meteoritic impacts). In the case of Jupiter, the sources of water could either be IDP or the SL9 comet impacts (Moses et al. 2000, Lellouch et al. 2002). The H2O submillimetric line at 557 GHz on Jupiter was detected by the SWAS satellite in 1999 and 2001 (Bergin et al. 2000, Lellouch et al. 2002) and by the Odin space telescope in 2002 with a high signal to noise ratio. The vertical profile and the column density previously derived from the SWAS observations (Bergin et al. 2000) were different from the one obtained from ISO measurements (Lellouch et al. 2002). SWAS measurements favored an IDP source, whereas ISO observations favored a SL9 source. We have re-analyzed SWAS data with the same approach we had for Odin data (Cavalié et al. 2006). Both origins for water supply have been modeled with our time-dependant photochemical model (Ollivier et al. 2000, adapted for Jupiter). The origin of water vapor in the stratosphere of Jupiter as suggested by our results will be discussed. References : Feuchtgruber et al. (1997), Nature, 389, 159-162. Feuchtgruber et al. (1999), The Universe as Seen by ISO. Eds. P. Cox & M. F. Kessler. ESA-SP, 427, 133. Lellouch et al. (1997), BAAS, 29, 992. Moses et al. (2000), Icarus, 145, 166-202. Lellouch et al. (2002), Icarus, 159, 112-131. Bergin et al. (2000), ApJ, 539, L147-L150. Ollivier et al. (2000), Plan. Space Sci., 48, 699-716. Cavalié et al. (2006), BAAS, 38, 497-498.
  09/2007; 39:414.
• Article: A three-dimensional simulation of transmitted light through planetary atmospheres using Monte-Carlo methods

  J Brillet, J ~P Parisot, M Dobrijevic, E Leflochmoen, D Toublanc
  Advances in Space Research 01/1996; 17:223-226. · 1.18 Impact Factor
• Article: Erratum: Photochemical modeling of Titan's Atmosphere (1995Icar..113....2T).

  D. Toublanc, J. P. Parisot, J. Brillet, D. Gautier, F. Raulin, C. P. McKay
  Icarus 08/1995; 117:218. · 3.38 Impact Factor
• Article: Photochemical modeling of Titan's atmosphere

  D Toublanc, J P Parisot, J Brillet, D Gautier, F Raulin, C P McKay
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  ABSTRACT: We have developed a new photochemical model of Titan's atmosphere which includes all the important compounds and reactions in spherical geometry from the surface to 1240 km. Compared to the previous model of Yung et al. (1984, Astrophys. J. Suppl. 55, 465-506), the most significant recent change in the reactions used is the updated methane photodissociation scheme (Mordaunt et al. 1993, J. Chem. Phys. 98(3), 2054-2065). Moreover, the transfer of the solar radiation in the atmosphere and the photolysis rates have been calculated by using a Monte Carlo code. Finally, the eddy diffusion coefficient profile is adjusted in order to fit the mean vertical distribution of HCN retrieved from millimeter groundbased observations of Tanguy et al. (1990, Icarus, 85, 43-57) using new values for the boundary flux of atomic nitrogen (Strobel et al. 1992, Icarus 100, 512-526). We have run the model in both steady-state and diurnal modes, with 62 speices involved in 249 reactions. There is little difference between diurnal and steady-state results. Overall our results are in a closer agreement with the abundances inferred from the Voyager infrared measurements at the equator than the Yung et al. results. We find that the catalytic scheme for H recombination invoked by Yung et al. only slightly improves the model results and we conclude that this scheme is not essential to fit observations.
  Icarus 02/1995; 113(1):2-26. · 3.38 Impact Factor
• Article: Diffusion à 3D dans l'atmosphère de Titan.

  M Dobrijevic, J Brillet, J -P Parisot, D Toublanc, D Gautier
  Journal des Astronomes Francais. 12/1993; 45:27-28.
• Article: Photochimie du mélange CH$_4$ - N$_2$. Application à l'atmosphère de Neptune.

  M Dobrijevic, J Brillet, J -P Parisot, D Gautier
  Journal des Astronomes Francais. 12/1993; 45:33.
• Article: Propriétés des aérosols dans l'atmosphère de Titan.

  J -P Parisot, J Brillet, M Dobrijevic, D Toublanc, D Gautier
  Journal des Astronomes Francais. 12/1993; 45:35-36.
• Article: Photochimie de l'atmosphère de Titan.

  J -P Parisot, J Brillet, M Dobrijevic, D Toublanc, D Gautier
  Journal des Astronomes Francais. 12/1993; 45:28.
• Source

  Available from: Michel Dobrijevic

  Conference Proceeding: Study of Transmitted Light Through Neptune's Atmosphere

  M Dobrijevic, T Morel, J ~P Parisot, J Brillet, D Gautier
  AAS/Division for Planetary Sciences Meeting Abstracts #25; 06/1993
• Source

  Available from: Michel Dobrijevic

  Conference Proceeding: Production and Distribution of the Aerosols in the Atmosphere of Titan

  M Dobrijevic, D Toublanc, J ~P Parisot, J Brillet
  AAS/Division for Planetary Sciences Meeting Abstracts #24; 06/1992
• Source

  Available from: Michel Dobrijevic

  Conference Proceeding: Three-Dimensional Simulation of Transmitted Light Through Titan's Atmosphere Using Monte-Carlo Methods

  M Dobrijevic, D Toublanc, J ~P Parisot, J Brillet, D Gautier
  AAS/Division for Planetary Sciences Meeting Abstracts #24; 06/1992