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Aviso Newsletter 7

January 2000


On August 10, 1999 the TOPEX/POSEIDON satellite celebrated its seventh year in operation. Just one day later, Paris, parts of Europe and the Middle East witnessed the breathtaking spectacle of a total solar eclipse. At the same time, the images of Earth sent back by French cosmonaut Jean-Pierre Haigneré from the Mir space station were an absolute feast for our eyes. The blue expanses that cover the majority of our ocean planet accompanied Jean-Pierre throughout his stay. The images he was able to acquire simply confirmed the ocean's vastness and incredible beauty. Its variations invite us to increase our efforts to understand it better and strengthen our desire to pursue our research. And whether we view the ocean through the naked eye or with the benefit of imaging instruments, only space-based observation can give us the global picture.

These three events dictated by celestial forces are a remarkable coincidence. Everyone who saw the total eclipse was struck not only by its stunning beauty, but also experienced a strong sense of belonging to the ballet of interacting celestial bodies taking place before our very eyes.

The interactions of the Earth, Moon and Sun underlie the phenomena we study. The ocean is where most of the energy received from the Sun is stored, transported and distributed around the globe. We now know that the Moon stabilizes the Earth's climate by keeping our planet's axis of rotation constant with respect to the ecliptic plane. Sun and Moon combine to generate the tides determined so accurately by TOPEX/POSEIDON (T/P). The unrivaled accuracy of long-term T/P measurements, to be continued by Jason-1 into the next century, has made it possible to finely distinguish the effects of the different tide components (we will be able to fully resolve unfavorably aliased constituents within two years!).

After the violent events that gave birth to our planet and its satellite, the Earth and Moon have now settled into a steady and well-established pattern. The total energy balance of the two bodies remains constant, but the Earth dissipates heat due to the friction of the tides. Its rotational velocity is also decreasing, with the result that the Moon is gradually being raised into a higher orbit at a rate of 3.6 centimeters a year. The Earth-Moon distance is measured by firing lasers from the Earth at four reflecting panels left on the surface of the Moon 30 years ago.

The summer of 1999 was also marked by many important technical milestones. Construction of the Jason satellite is well under way. Almost all the bus ancillary systems and payload instruments have been installed. Initial test results have confirmed that performance targets will be met. A good deal of work now lies ahead of us to test and validate the satellite with the ground segment components in all possible configurations to ready the satellite for launch.

Philippe Escudier, Patrick Vincent, Michel Lefèbvre


Editorial board: Patrick Vincent (CNES), Yves Ménard (CNES), Vinca Rosmorduc (CLS)

Authors and other contributors: J. Ballabrera, F. Barlier, F. Blanc, R. Boain, P. Bonnefond, G. Born, G. Boutonnet, P. Brasseur, A. J. Busalacchi, S. Coutin-Faye, T. Delacroix, J. Dorandeu, P. Escudier, P. Exertier, L. Fenoglio-Marc, L. L. Fu, L. Gourdeau, E. Groten, T. H. Guymer, B. Haines, P. Hoze, E. Jeansou, G. Julien, S. Kaki, D. Kubitschek, G. Kunstmann, T. Lafon, M.-H. de Launay, O. Laurain, M. Lefèbvre, F. Mertz, R. Murtugudde, J. Noubel, A. Orsoni, L. Parent, F. Parisot, N. Picot, G. D. Quartly, M. A. Srokosz, C. E. Testut, V. Valette, J. Verron, Y. Wang.

English adaptation: B. Vincent

Design: D. Ducros

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