Plus d'un millier d'exoplanètes ont été découvertes depuis une dizaine d'années. Plus incroyable encore, nous pouvons maintenant caractériser les atmosphères de ces mondes lointains. Des spectres de Jupiter-chauds tels que HD 189733b et HD 209458b et de planètes similaires à Neptune telles que GJ1214b sont déjà disponibles et ceux de planètes plus petites le seront bientôt. La plupart des observations caractérisent l'état moyen de l'atmosphère. Pour les cas les plus favorables, l'observation des courbes de phase et la technique de cartographie par éclipse secondaire permettent d'obtenir une résolution en longitude et en latitude. Les planètes les plus proches de leurs étoiles sont aussi les plus faciles à observer. Ces mondes chauds sont radicalement différents des exemples que nous avons dans le système solaire. Modéliser correctement leurs atmosphères est un défi à relever pour comprendre les observations présentes et à venir. Durant cette thèse, j'ai développé des modèles de différente complexité pour comprendre les interactions entre la structure thermique, la composition, la circulation atmosphérique et l'évolution à long terme des exoplanètes irradiées. La forte luminosité de leur étoile hôte détermine le climat de ces planètes. Elle engendre une circulation atmosphérique qui maintient l'atmosphère dans un état de déséquilibre thermique et chimique, affectant son évolution. Avec les futurs instruments de nombreuses autres planètes vont être découvertes et caractérisées. Nos modèles seront testés sur une large diversité de planètes, ouvrant les portes de la climatologie aux exoplanètes.

On December 30th 2000, the Cassini-Huygens spacecraft reached the perijove milestone in its continuing journey to the Saturnian system. During an extended six-month encounter, the Composite Infrared Spectrometer (CIRS) returned spectra of the Jovian atmosphere, rings and satellites from 10 to 1400 cm^-1 (1000 to 7 µm) at a programmable spectral resolution of 0.5 to 15 cm^-1. The improved spectral resolution of CIRS over previous infrared instrument-missions to Jupiter, the extended spectral range and higher signal-to-noise performance provide significant advantages over previous data-sets. Both optimal-estimation retrieval and radiance-differencing are used to investigate the global variation of upper-tropospheric temperature, ammonia, phosphine and cloud opacity between ± 60˚ latitude. The analysis methods are shown to successfully reproduce Jovian conditions with results consistent with previous investigations. The composition results in particular are well characterised and suggest an important role played by mixing and transport within the upper-troposphere. Interpretation and validation of the retrieved results is conducted via the construction of a simple dynamic model incorporating transport, diffusion and (photo)chemistry.

The object of this research program has been to provide a baseline for microwave remote sensing of ammonia and water vapor in the atmosphere of Jupiter through laboratory measurements of their microwave absorption properties. Jupiter is not only the largest planet in our solar system, but one of the most interesting and complex. Despite a handful of spacecraft missions and many astronomical measurements, much of Jupiter s atmospheric dynamics and composition remain a mystery. Although constraints have been formed on the amount of certain gases present, the global abundances and distributions of water vapor (H2O) and ammonia (NH3) are relatively unknown. Measurements of H2O and NH3 in the Jovian atmosphere to hundreds of bars of pressure are best accomplished via passive microwave emission measurements. For these measurements to be accurately interpreted, however, the hydrogen and helium pressure-broadened microwave opacities of H2O and NH3 must be well characterized, a task that is very difficult if based solely on theory and limited laboratory measurements. Therefore, accurate laboratory measurements have been taken under a broad range of conditions that mimic those of the Jovian atmosphere. These measurements, performed using a newly redesigned high-accuracy system, and the corresponding models of microwave opacity that have been developed from them comprise the majority of this work. The models allow more accurate retrievals of H2O and NH3 abundances from previous as well as future missions to Jupiter and the outer planets, such as the NASA New Frontiers class Juno mission scheduled for launch in 2011. This information will enable a greater understanding of the concentration and distribution of H2O and NH3 in the Jovian atmosphere, which will reveal much about how Jupiter and our solar system formed and how similar planets could form in other solar systems, even planets that may be hospitable to life.

Heidelberg, Univ., Diss., 2007.

Astronomers have been observing the night sky for many centuries to establish a better understanding for our universe and solar system. As part of their observations, astronomers characterize celestial bodies by fundamental properties such as mass, motion, and composition in order to provide further insight about the objects in question. As technology and science have evolved, the methods for measuring these properties have become more precise and accurate. One such methodology is known as spectroscopy, and it is a significant tool for observational astronomy. In this paper, we shall describe how we used astronomical spectroscopy to determine orbital and rotational velocities for various objects in our solar system. This method was implemented specifically using the facilities of the Harry D. Powell Observatory on the campus of East Tennessee State University.

Observations of Jupiter show a super-rotating (prograde) equatorial jet that has persisted for decades. Shallow water simulations run in the Jovian parameter regime reproduce the mixture of robust vortices and alternating zonal jets observed on Jupiter, but the equatorial jet is invariably sub-rotating (retrograde). Recent work has obtained super-rotating equatorial jets by extending the standard shallow water equations to relax the height field towards its mean value. This Newtonian cooling-like term is intended to model radiative cooling to space, but its addition breaks key conservation properties for mass and momentum. In this thesis the radiatively damped thermal shallow water equations are proposed as an alternative model for Jovian atmospheres. They extend standard shallow water theory by permitting horizontal variations of the thermodynamic properties of the fluid. The additional temperature equation allows a Newtonian cooling term to be included while conserving mass and momentum. Simulations reproduce equatorial jets in the correct directions for both Jupiter and Neptune (which sub-rotates). Quasi-geostrophic theory filters out rapidly moving inertia-gravity waves. A local quasi-geostrophic theory of the radiatively damped thermal shallow water equations is derived, and then extended to cover whole planets. Simulations of this global thermal quasi-geostrophic theory show the same transition, from sub- to super-rotating equatorial jets, seen in simulations of the original thermal shallow water model as the radiative time scale is decreased. Thus the mechanism responsible for setting the direction of the equatorial jet must exist within quasi-geostrophic theory. Such a mechanism is developed by calculating the competing effects of Newtonian cooling and Rayleigh friction upon the zonal mean zonal acceleration induced by equatorially trapped Rossby waves. These waves transport no momentum in the absence of dissipation. Dissipation by Newtonian cooling creates an eastward zonal mean zonal acceleration, consistent with the formation of super-rotating equatorial jets in simulations, while the corresponding acceleration is westward for dissipation by Rayleigh friction.

The Jupiter Icy Moons Explorer is a planetary exploration mission that aims to study the moons of Jupiter in the planet’s vast magnetosphere. Among the various instruments on board is the Particle Environment Package (PEP), that is led by the Swedish Institute of Space Physics (IRF) in Kiruna. The Jovian plasma Dynamics and Composition analyzer (JDC) is one of six sensors within PEP and focuses on the characterization of positive ions. To be able to measure their three-dimensional distribution and composition, in-situ and in high time resolution, JDC has to cover a large field of view of 2π sr, for the desired energy range, in just a couple of seconds. An electrostatic analyzer within the sensor determines the energy per charge of such particles and a time-of-flight mass spectrometer measures their mass per charge. Constraints on weight and the radiation environment of Jupiter drive the design of the sensor: small and lightweight to allow extra shielding, but still large enough to accomplish measurements in the harsh radiation environment of Jupiter. This work focuses on a new type of compact, electrostatic analyzer using spherical wedges and the start signal generation for the time-of-flight measurement using new venetian blind-type surfaces. Simulations on the electrostatic analyzer showed that the most promising design is a hybrid variant, using an inner shell with spherical wedges and a spheroidal outer shell. A prototype sensor was built and tested with successful results. A reflectron-type time-of-flight cell measures the time it takes for a particle to pass a linear electric field. The time measurement has to be very accurate and requires that all ions enter the reflectron from the same start position. Commonly this is achieved with thin carbon foils of some nanometer thickness to provide a very accurate start position. Upon impact and after leaving a foil, ions generate secondary electrons that act as start signals for the time measurement. Foils require a substantial pre-acceleration of several kilovolts for the ions to penetrate the foil, thus increasing the size and mass of the instrument. When incident ions are reflected at grazing angles from a surface, secondary electrons are released in the same way as with foils. To increase position accuracy during this reflection process, venetian blind-type start surfaces are investigated, where many smaller surfaces replace a large flat surface. The most promising sample was found to be micro pore optics, that were initially designed to focus gamma rays. In several experiments it could be shown that micro pore optics show good reflection properties when used as start surfaces in the time-of-flight measurement. Both improvements allow a more compact and lightweight sensor that can be better shielded against the harsh radiation environment in Jupiter’s system. Jupiter hosts the strongest radiation environment in the solar system, that could kill an unprotected human thousand times over. / JUICE, PEP

L'étude du rayonnement UV de la haute atmosphère des planètes géantes ne peut se faire qu'à l'aide de techniques de transfert radiatif. Ces hautes atmosphères étant constituées essentiellement d'hydrogène, il convient d'étudier les raies de la série de Lyman de l'hydrogène atomique. Cependant, la présence dans ces atmosphères, de H et de H2, génère des chevauchements, entre les raies de la série de Lyman et les bandes de l'hydrogène moléculaire. Nous avons modélisé les effets de ces chevauchements pour les raies Lyman alpha, beta et gamma. On constate que ces effets sont souvent importants surtout à cause de l'auto-absorption des raies dues à H2 à la fois sur Jupiter et Saturne. On peut obtenir via cette méthode, des informations sur l'état et les concentrations de l'hydrogène moléculaire et atomique, en particulier les températures vibrationnelles de l'hydrogène moléculaire. Cette technique pourra être étendue aux zones aurorales et éventuellement aux planètes extrasolaires.

Plus de 300 planètes extrasolaires ont été découvertes à ce jour. La variété et la diversité des caractéristiques qu'elles présentent sont extrêmement vastes. Et dans cette multitude, une population se distingue, les Jupiter-chauds. Ces planètes ne ressemblent, en effet, en rien à celles que l'on côtoie dans le Système Solaire. Elles ont une masse d'une à plusieurs fois celle de Jupiter et sont très proches de leur étoile parent, orbitant en seulement quelques jours. L'étude de cette population nous apporte beaucoup d'éléments quant à leur processus de formation et d'évolution. Certaines d'entre elles ont en effet la particularité de transiter devant leur étoile parent. Mes travaux de thèse m'ont mené à détecter et caractériser en densité 14 planètes extrasolaires, grâce aux programmes de recherche CoRoT et SuperWASP combinés au spectrographe SOPHIE (OHP). Parmi ces planètes figurent celles ayant la plus courte période orbitale et, autour d'une autre étoile, la plus importante masse jamais détectées en transit. Un programme novateur, que j'ai initié, nous a également permis d'explorer les capacités de détection d'un instrument de type multi-fibre (FLAMES/GIRAFFE et UVES). Nous avons montré que cet instrument peut être performant en terme de précision de mesure en vitesse radiale, et qu'il permet un très bon écrémage des cibles. L'instrument multi-fibre est utilisable également dans le cadre d'un suivi de candidats issus de programmes de recherche par photométrie, tels que la mission CoRoT , mais il nécessite dans ce cas, pour être eficace, d'un champ de vue significatif (de plusieurs degrés carrés par exemple). L'étude du transit spectroscopique de 3 systèmes planétaires m'a également permis d'apporter de fortes contraintes quant à leur processus de formation et d'évolution, et de mettre en évidence pour la première fois l'existence d'un système exotique : X0-3.

Most studies of Roman architecture cover the third century BCE to the fourth century CE, a period of luxurious building projects like the Colosseum and Pantheon that remain relatively well documented in the archaeological and literary record. Yet Rome did not spring fully formed from the ground in the third century, its architecture relying entirely on precursors and precedents in buildings from far away times and places. In this study I fit remains of architecture from early Rome (ca. 650 to 450 BCE) into the cultural framework of the contemporaneous Mediterranean and try to assess how the changing cityscape effected both archaic Romans and later Roman architecture and topography. Because many studies of archaic Rome have attempted to fit archaeological remains with the literary record, and because this has created much controversy, I put the literary record to one side and focus on material remains in an attempt to see what they can reveal on their own.