BARLIER , F.

La Terre est tout à la fois l'habitat de l'Homme et un fragment de l'Univers. Cette double nature imprime un caractère particulier aux efforts faits pour la connaître. Les progrès de sa connaissance s'intègrent dans ceux des sciences de l'Univers, ils répondent aussi aux besoins matériels de l'Homme : ils éclairent sa relation à la Terre....

he Earth is surrounded by a layer of relatively thin gas, the mass of which is mainly concentrated in the first kilometres. With an exponential decrease of the density of the atmosphere as a function of altitude, 99.9% of this mass is located in the first 50 km. In addition, the composition of major species is homogeneous up to about 85 km,...

Le projet européen Galileo est un enjeu majeur pour le développement économique et la sécurité de l'Europe. La construction d'un outil de repère spatiotemporel sur la Terre et dans son environnement, en faisant appel aux techniques spatiales (satellites), n'est pas une entreprise occasionnelle ; c'est une évolution majeure et irréversible du...

Comptes Rendus Géoscience, v. 337, n. 14, p. 1223-1224, 2005. http://dx.doi.org/10.1016/j.crte.2005.07.007

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Advances in Space Research, v. 36, n. 3, p. 402-411, 2005. http://dx.doi.org/10.1016/j.asr.2005.04.056

This paper aims at investigating the stability over 150 years of a very large number of trajectories in the Medium Earth Orbit (MEO) region, near the orbits devoted to radionavigation such as the Global Navigation Satellite Systems (GNSS like GPS, Glonass, Galileo, COMPASS). The stability is characterized by the long term evolution of the...

Advances in Space Research, v. 36, n. 3, p. 522-533, 2005. http://dx.doi.org/10.1016/j.asr.2005.03.029

International audience

Averaging methods are convenient tools for studying long-periodic variations of the motion of artificial satellites. The main lines of a semi-analytical theory of the mean motion are given. We show how, when coupled with a careful reduction of the tracking data, this theory allows to determine parameters related to the temporal variations of...

A large volume of data (temperatures, densities, concentrations, winds, etc.) has been accumulated showing that in addition to seasonal changes in the thermosphere, annual variations are present and have a component that is a function of latitude. It appears that the helium concentrations have much larger variations in the southern hemisphere...

Comptes Rendus Géoscience, v. 338, n. 14-15, p. 958-967, 2006. http://dx.doi.org/10.1016/j.crte.2006.09.019

The Western Alps are among the best studied collisional belts with both detailed structural mapping and also crustal geophysical investigations such as the ECORS and EGT seismic profile. By contrast, the present-day kinematics of the belt is still largely unknown due to small relative motions and the insufficient accuracy of the triangulation...

Tahiti is a unique geodetic site located in the south Pacific Ocean where few observatories exist nearby. The American mobile station MOBLAS-8 was installed in Tahiti in 1998, and GPS and DORIS systems were also deployed in its vicinity in order to develop this site into one of the fundamental colocated sites of the International Terrestrial...

Satellite Laser Ranging (SLR) began in the mid-1960s on satellites of opportunity with retro-reflectors intended as a part of intercomparison tests of satellite tracking techniques. Shortly thereafter, data from these satellites began to work their way into geodetic solutions and dedicated geodesy experiments. By early 1970s when future...