December 3, 2004
Colloquium Topic: Cassini at Saturn: Wonders of the Giant Planet Revisited
The first encounter of Saturn by a spacecraft occurred in 1979, when Pioneer-11 was retargeted as an afterthought from a flyby of Jupiter in 1974. Pioneer discovered the magnetosphere of the planet, but was not equipped to image Saturn and its moons in any detail. The encounters by Voyager-1 in 1980 and Voyager-2 in 1981 revealed a truly majestic planet with spectacular rings and the biggest satellite in the solar system, Titan, shrouded by a thick atmosphere some 50% thicker than that of Earth's, making it impossible to image the moon's surface. The magnetosphere was found to be quite variable and contain hot plasma at temperatures of hundreds of millions of degrees, as determined from the APL instrument on those spacecraft. Cassini, launched in October 1997, arrived at Saturn on July 1 this year carrying a comprehensive payload of instruments including the APL-built Magnetospheric Imaging Instrument (MIMI), and a Synthetic Aperture Radar (SAR) designed to peer through Titan's smog and image the surface. The data so far have been exceptional. Some findings include waves in the rings, new moons, many water products floating way past the rings, several mysterious features on Titan's surface and atmosphere, and a magnetosphere that is co-rotating with the planet. This is only the beginning of a four-year tour that will involve some forty-four close encounters (down to ~900 km altitude) with Titan, and the release of the ESA-built Huygens probe that will float through Titan's atmosphere on January 14, 2005 to a hoped-for soft landing on that moon's surface, whether solid or liquid.
Colloquium Speaker: Stamatios M. Krimigis
Dr. Stamatios (Tom) Krimigis has been at APL since 1968, after earning his B. Physics from the University of Minnesota (1961), and his M.S. (1963) and Ph.D. (1965) in Physics from the University of Iowa and serving as Assistant Professor of Physics and Astronomy there. He became Supervisor of Space Physics and Instrumentation in the Space Department, Chief Scientist in 1980, Department Head in 1991, and Emeritus Head in 2004. He is Principal Investigator on several NASA spacecraft, including Voyagers 1 and 2 to the Outer Planets and the Voyager Interstellar Mission, and the Cassini mission to Saturn and Titan. He has designed and built instruments that have flown to seven of the nine planets, and hopes to complete the set with his participation in the MESSENGER mission to Mercury and New Horizons mission to Pluto. He has published more than 370 papers in journals and books on the physics of the sun, interplanetary medium, planetary magnetospheres, and the heliosphere. He is recipient of NASA's Exceptional Scientific Achievement Medal twice, is a Fellow of the American Physical Society, American Geophysical Union, and American Association for the Advancement of Science, recipient of COSPAR's Space Science Award in 2002, a recipient of the Basic Sciences Award of the International Academy of Astronautics where he serves on the Board of Trustees, and was elected recently to the newly established chair of "Science of Space" of the Academy of Athens.