T. Encrenaz - Academia.edu (original) (raw)

Papers by T. Encrenaz

Research paper thumbnail of Millimeter and submillimeter measurements of asteroid (2867) Steins during the Rosetta fly-by

Planetary and Space Science

The European Space Agency Rosetta Spacecraft passed within 803 km of the main belt asteroid (2867... more The European Space Agency Rosetta Spacecraft passed within 803 km of the main belt asteroid (2867) Steins on 5 September 2008. The Rosetta Spacecraft carries a number of scientific instruments including a millimeter and submillimeter radiometer and spectrometer. The instrument, named MIRO (Microwave Instrument for the Rosetta Orbiter), consists of a 30-cm diameter, offset parabolic reflector telescope followed by two heterodyne receivers. Center-band operating frequencies of the receivers are near 190 GHz (1.6 mm) and 562 GHz (0.53 mm). Broadband continuum channels are implemented in both frequency bands for the measurement of near surface temperatures and temperature gradients. A 4096 channel CTS (chirp transform spectrometer) having 180 MHz total bandwidth and $ 44 kHz resolution is also connected to the submillimeter receiver. We present the continuum observations of asteroid (2867) Steins obtained during the fly-by with the MIRO instrument. Spectroscopic data were also collected during the fly-by using the MIRO spectrometer fixed-tuned to rotational lines of several molecules. Results of the spectroscopic investigation will be the topic of a separate publication. Comparative thermal models and radiative transfer calculations for Steins are presented. Emissivities of Steins were determined to be 0.6-0.7 and 0.85-0.9 at wavelengths of 0.53 and 1.6 mm, respectively. The thermal inertia of Steins was estimated to be in the range 450-850 J/(m 2 s 0.5 K). Assuming that the emissivity of Steins is determined by the Fresnel reflection coefficients of the surface material, the area-averaged dielectric constant of the surface material is in the range 4-20. These values are rock-like, and are unlike the powdered-regolith surface of the Moon.

Research paper thumbnail of Hydrogen peroxide on Mars: Observations, interpretation and future plans

Planetary and Space Science

... to be in better agreement with the low upper limit inferred by Herschel/HIFI at Ls ... The ge... more ... to be in better agreement with the low upper limit inferred by Herschel/HIFI at Ls ... The general trend of the observations is in reasonable agreement with the predictions of the ... In the future, hydrogen peroxide on Mars should be detectable with the infrared spectrometer MATMOS ...

Research paper thumbnail of Quelques aspects de la dynamique des atmosphères des planètes géantes

Contents: 1. La répartition des vents sur Jupiter et Saturne: Equation du vent thermique. Equatio... more Contents: 1. La répartition des vents sur Jupiter et Saturne: Equation du vent thermique. Equation du vent géostrophique. Ondes Rossby. 2. Revue des modèles d'atmosphére de Jupiter: Modèle d'instabilité radiatif/convectif. Modèle convectif axisymétrique. Modèle de cascade turbulente à deux dimensions. Modèle de convection en rouleaux. 3. Analyse du profile en latitude des vents.

Research paper thumbnail of Acetylene, Ethane and Polar Infrared Brightening on Jupiter

Research paper thumbnail of The 3-5 μ m Spectrum of Uranus: Constraints on H3+, CO and PH3

Research paper thumbnail of SWS spectroscopy of planets

Research paper thumbnail of Element Abundances and Isotope Ratios in the Giant Planets and Titan

Space Sciences Series of ISSI, 2003

This paper reviews our present knowledge about elemental and isotopic ratios in the Giant Planets... more This paper reviews our present knowledge about elemental and isotopic ratios in the Giant Planets and Titan. These parameters can provide key information about the formation and evolution of these objects. Element abundances, especially after the results of the Galileo Probe Mass Spectrometer in Jupiter, strongly support the formation model invoking an initial core formation (Mizuno, 1980; Pollack et al., 1996). They also suggest that solar composition icy planetesimals (SCIPs) brought the heavy elements to Jupiter. The Jupiter value of D/H appears to be representative of the protosolar value, while the D/H enrichment observed on Uranus and Neptune is consistent with the formation scenario of these planets. The 15N/14N measurement in Jupiter seems to be representative of its protosolar value. Future measurements are expected to come from the Cassini and Herschel space mission, as well as the ALMA submillimeter observatory.

Research paper thumbnail of High-Resolution Observation of the 2.3 Micron CO Band on Mars

Research paper thumbnail of Search for Local Variations of Atmospheric H2O and CO on Mars with PFS/Mars Express

Research paper thumbnail of Observations of methane emission at 3 microns with the ESO NTT at the time of the SL9 H impact

Research paper thumbnail of Wind measurements in Mars' middle atmosphere at equinox and solstice: IRAM Plateau de Bure interferometric CO observations

Research paper thumbnail of Detection of methyl radicals (CH_3) on Saturn

Astronomy and Astrophysics

... We report the first detection ofmethylradicals (CH3) in the upper atmosphere of Saturn. ... 1... more ... We report the first detection ofmethylradicals (CH3) in the upper atmosphere of Saturn. ... 1996; Romani et al. 1993). The importance of the methyl radical (CH3) as an intermediate in the hydrocarbon photochemistry prompted us to search for its presence in Saturn and Neptune. ...

Research paper thumbnail of Latitudinal variations of minor species in the atmosphere of Venus from ground-based observations

Research paper thumbnail of Solar System History from Isotopic Signatures of Volatile Elements

Research paper thumbnail of Mid-IR Observations of Uranus’ H2 Quadrupole Emission Near Equinox

The dominant process causing the high thermospheric temperatures observed for the major planets r... more The dominant process causing the high thermospheric temperatures observed for the major planets remains an unsolved problem. Uranus is of particular interest for identifying this source of heating because of its extreme obliquity and weak internal heat source, which permit large seasonal extremes driven by radiative and dynamical processes. Sources of thermospheric heating may be investigated indirectly through the energy balance of the offsetting line emission, which radiates the generated heat to space. The cooling rate can be characterized by observing the line emission vs. position over the planet. The primary coolant in Uranus’ thermosphere is emission in the rotational H2 quadrupole lines. We report observations of Uranus’ rotational H2 quadrupole line emission obtained near the 2007 equinox using TEXES at Gemini in late October, 2007. Good data were obtained for the H2 S(1) line, which was scanned longitudinally across Uranus’ disk to make an emission map showing all latitude...

Research paper thumbnail of Seasonal variations of hydrogen peroxide and water vapor on Mars: Further indications of heterogeneous chemistry

Astronomy & Astrophysics, 2015

We have completed our seasonal monitoring of hydrogen peroxide and water vapor on Mars using grou... more We have completed our seasonal monitoring of hydrogen peroxide and water vapor on Mars using ground-based thermal imaging spectroscopy, by observing the planet in March 2014, when water vapor is maximum, and July 2014, when, according to photochemical models, hydrogen peroxide is expected to be maximum. Data have been obtained with the Texas Echelon Cross Echelle Spectrograph (TEXES) mounted at the 3 m-Infrared Telescope Facility (IRTF) at Maunakea Observatory. Maps of HDO and H 2 O 2 have been obtained using line depth ratios of weak transitions of HDO and H 2 O 2 divided by CO 2. The retrieved maps of H 2 O 2 are in good agreement with predictions including a chemical transport model, for both the March data (maximum water vapor) and the July data (maximum hydrogen peroxide). The retrieved maps of HDO are compared with simulations by Montmessin et al. (2005, J. Geophys. Res., 110, 03006) and H 2 O maps are inferred assuming a mean martian D/H ratio of 5 times the terrestrial value. For regions of maximum values of H 2 O and H 2 O 2 , we derive, for March 1 2014 (Ls = 96 •), H 2 O 2 = 20 +/− 7 ppbv, HDO = 450 +/− 75 ppbv (45 +/− 8 pr-nm), and for July 3, 2014 (Ls = 156 •), H 2 O 2 = 30 +/− 7 ppbv, HDO = 375 +/− 70 ppbv (22 +/− 3 pr-nm). In addition, the new observations are compared with LMD global climate model results and we favor simulations of H 2 O 2 including heterogeneous reactions on water-ice clouds.

Research paper thumbnail of Shoemaker?Levy 9?Jupiter Collision

The Encyclopedia of Astronomy and Astrophysics, 2001

The collision of comet Shoemaker-Levy 9 (SL9) with JUPITER, in July 1994, was an exceptional even... more The collision of comet Shoemaker-Levy 9 (SL9) with JUPITER, in July 1994, was an exceptional event for astronomers who were able to watch in real time the response of a planetary atmosphere to a large meteoritic impact. A wide variety of phenomena were observed such as temperature increase in the stratosphere, formation of aerosols and new gaseous species, and changes in the magnetosphere. Some o...

Research paper thumbnail of High Spatial Resolution Spectra of Comet Iras-Aracki-Alcock (1983 d)

Research paper thumbnail of Light elements in the Solar system

Conference on 3K cosmology, 1999

Research paper thumbnail of Results of infrared spectrometer experiment. 1: Infrared radiation of parent molecules in Halley's Comet

The infrared spectrometer experiment was for solving two problems: registry of IR emissions of pa... more The infrared spectrometer experiment was for solving two problems: registry of IR emissions of parent molecules in the coma surrounding the nucleus and research on the IR emission of the nucleus. Here, research on the parent nucleus is examined. The results obtained as of May 1987 are summarized. The technical specifications of the IR spectrometer are given, and the procedure

Research paper thumbnail of Millimeter and submillimeter measurements of asteroid (2867) Steins during the Rosetta fly-by

Planetary and Space Science

The European Space Agency Rosetta Spacecraft passed within 803 km of the main belt asteroid (2867... more The European Space Agency Rosetta Spacecraft passed within 803 km of the main belt asteroid (2867) Steins on 5 September 2008. The Rosetta Spacecraft carries a number of scientific instruments including a millimeter and submillimeter radiometer and spectrometer. The instrument, named MIRO (Microwave Instrument for the Rosetta Orbiter), consists of a 30-cm diameter, offset parabolic reflector telescope followed by two heterodyne receivers. Center-band operating frequencies of the receivers are near 190 GHz (1.6 mm) and 562 GHz (0.53 mm). Broadband continuum channels are implemented in both frequency bands for the measurement of near surface temperatures and temperature gradients. A 4096 channel CTS (chirp transform spectrometer) having 180 MHz total bandwidth and $ 44 kHz resolution is also connected to the submillimeter receiver. We present the continuum observations of asteroid (2867) Steins obtained during the fly-by with the MIRO instrument. Spectroscopic data were also collected during the fly-by using the MIRO spectrometer fixed-tuned to rotational lines of several molecules. Results of the spectroscopic investigation will be the topic of a separate publication. Comparative thermal models and radiative transfer calculations for Steins are presented. Emissivities of Steins were determined to be 0.6-0.7 and 0.85-0.9 at wavelengths of 0.53 and 1.6 mm, respectively. The thermal inertia of Steins was estimated to be in the range 450-850 J/(m 2 s 0.5 K). Assuming that the emissivity of Steins is determined by the Fresnel reflection coefficients of the surface material, the area-averaged dielectric constant of the surface material is in the range 4-20. These values are rock-like, and are unlike the powdered-regolith surface of the Moon.

Research paper thumbnail of Hydrogen peroxide on Mars: Observations, interpretation and future plans

Planetary and Space Science

... to be in better agreement with the low upper limit inferred by Herschel/HIFI at Ls ... The ge... more ... to be in better agreement with the low upper limit inferred by Herschel/HIFI at Ls ... The general trend of the observations is in reasonable agreement with the predictions of the ... In the future, hydrogen peroxide on Mars should be detectable with the infrared spectrometer MATMOS ...

Research paper thumbnail of Quelques aspects de la dynamique des atmosphères des planètes géantes

Contents: 1. La répartition des vents sur Jupiter et Saturne: Equation du vent thermique. Equatio... more Contents: 1. La répartition des vents sur Jupiter et Saturne: Equation du vent thermique. Equation du vent géostrophique. Ondes Rossby. 2. Revue des modèles d'atmosphére de Jupiter: Modèle d'instabilité radiatif/convectif. Modèle convectif axisymétrique. Modèle de cascade turbulente à deux dimensions. Modèle de convection en rouleaux. 3. Analyse du profile en latitude des vents.

Research paper thumbnail of Acetylene, Ethane and Polar Infrared Brightening on Jupiter

Research paper thumbnail of The 3-5 μ m Spectrum of Uranus: Constraints on H3+, CO and PH3

Research paper thumbnail of SWS spectroscopy of planets

Research paper thumbnail of Element Abundances and Isotope Ratios in the Giant Planets and Titan

Space Sciences Series of ISSI, 2003

This paper reviews our present knowledge about elemental and isotopic ratios in the Giant Planets... more This paper reviews our present knowledge about elemental and isotopic ratios in the Giant Planets and Titan. These parameters can provide key information about the formation and evolution of these objects. Element abundances, especially after the results of the Galileo Probe Mass Spectrometer in Jupiter, strongly support the formation model invoking an initial core formation (Mizuno, 1980; Pollack et al., 1996). They also suggest that solar composition icy planetesimals (SCIPs) brought the heavy elements to Jupiter. The Jupiter value of D/H appears to be representative of the protosolar value, while the D/H enrichment observed on Uranus and Neptune is consistent with the formation scenario of these planets. The 15N/14N measurement in Jupiter seems to be representative of its protosolar value. Future measurements are expected to come from the Cassini and Herschel space mission, as well as the ALMA submillimeter observatory.

Research paper thumbnail of High-Resolution Observation of the 2.3 Micron CO Band on Mars

Research paper thumbnail of Search for Local Variations of Atmospheric H2O and CO on Mars with PFS/Mars Express

Research paper thumbnail of Observations of methane emission at 3 microns with the ESO NTT at the time of the SL9 H impact

Research paper thumbnail of Wind measurements in Mars' middle atmosphere at equinox and solstice: IRAM Plateau de Bure interferometric CO observations

Research paper thumbnail of Detection of methyl radicals (CH_3) on Saturn

Astronomy and Astrophysics

... We report the first detection ofmethylradicals (CH3) in the upper atmosphere of Saturn. ... 1... more ... We report the first detection ofmethylradicals (CH3) in the upper atmosphere of Saturn. ... 1996; Romani et al. 1993). The importance of the methyl radical (CH3) as an intermediate in the hydrocarbon photochemistry prompted us to search for its presence in Saturn and Neptune. ...

Research paper thumbnail of Latitudinal variations of minor species in the atmosphere of Venus from ground-based observations

Research paper thumbnail of Solar System History from Isotopic Signatures of Volatile Elements

Research paper thumbnail of Mid-IR Observations of Uranus’ H2 Quadrupole Emission Near Equinox

The dominant process causing the high thermospheric temperatures observed for the major planets r... more The dominant process causing the high thermospheric temperatures observed for the major planets remains an unsolved problem. Uranus is of particular interest for identifying this source of heating because of its extreme obliquity and weak internal heat source, which permit large seasonal extremes driven by radiative and dynamical processes. Sources of thermospheric heating may be investigated indirectly through the energy balance of the offsetting line emission, which radiates the generated heat to space. The cooling rate can be characterized by observing the line emission vs. position over the planet. The primary coolant in Uranus’ thermosphere is emission in the rotational H2 quadrupole lines. We report observations of Uranus’ rotational H2 quadrupole line emission obtained near the 2007 equinox using TEXES at Gemini in late October, 2007. Good data were obtained for the H2 S(1) line, which was scanned longitudinally across Uranus’ disk to make an emission map showing all latitude...

Research paper thumbnail of Seasonal variations of hydrogen peroxide and water vapor on Mars: Further indications of heterogeneous chemistry

Astronomy & Astrophysics, 2015

We have completed our seasonal monitoring of hydrogen peroxide and water vapor on Mars using grou... more We have completed our seasonal monitoring of hydrogen peroxide and water vapor on Mars using ground-based thermal imaging spectroscopy, by observing the planet in March 2014, when water vapor is maximum, and July 2014, when, according to photochemical models, hydrogen peroxide is expected to be maximum. Data have been obtained with the Texas Echelon Cross Echelle Spectrograph (TEXES) mounted at the 3 m-Infrared Telescope Facility (IRTF) at Maunakea Observatory. Maps of HDO and H 2 O 2 have been obtained using line depth ratios of weak transitions of HDO and H 2 O 2 divided by CO 2. The retrieved maps of H 2 O 2 are in good agreement with predictions including a chemical transport model, for both the March data (maximum water vapor) and the July data (maximum hydrogen peroxide). The retrieved maps of HDO are compared with simulations by Montmessin et al. (2005, J. Geophys. Res., 110, 03006) and H 2 O maps are inferred assuming a mean martian D/H ratio of 5 times the terrestrial value. For regions of maximum values of H 2 O and H 2 O 2 , we derive, for March 1 2014 (Ls = 96 •), H 2 O 2 = 20 +/− 7 ppbv, HDO = 450 +/− 75 ppbv (45 +/− 8 pr-nm), and for July 3, 2014 (Ls = 156 •), H 2 O 2 = 30 +/− 7 ppbv, HDO = 375 +/− 70 ppbv (22 +/− 3 pr-nm). In addition, the new observations are compared with LMD global climate model results and we favor simulations of H 2 O 2 including heterogeneous reactions on water-ice clouds.

Research paper thumbnail of Shoemaker?Levy 9?Jupiter Collision

The Encyclopedia of Astronomy and Astrophysics, 2001

The collision of comet Shoemaker-Levy 9 (SL9) with JUPITER, in July 1994, was an exceptional even... more The collision of comet Shoemaker-Levy 9 (SL9) with JUPITER, in July 1994, was an exceptional event for astronomers who were able to watch in real time the response of a planetary atmosphere to a large meteoritic impact. A wide variety of phenomena were observed such as temperature increase in the stratosphere, formation of aerosols and new gaseous species, and changes in the magnetosphere. Some o...

Research paper thumbnail of High Spatial Resolution Spectra of Comet Iras-Aracki-Alcock (1983 d)

Research paper thumbnail of Light elements in the Solar system

Conference on 3K cosmology, 1999

Research paper thumbnail of Results of infrared spectrometer experiment. 1: Infrared radiation of parent molecules in Halley's Comet

The infrared spectrometer experiment was for solving two problems: registry of IR emissions of pa... more The infrared spectrometer experiment was for solving two problems: registry of IR emissions of parent molecules in the coma surrounding the nucleus and research on the IR emission of the nucleus. Here, research on the parent nucleus is examined. The results obtained as of May 1987 are summarized. The technical specifications of the IR spectrometer are given, and the procedure