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SwRI ion and electron sensor successfully commissioned for operation aboard ESA Rosetta comet orbiter

San Antonio -- September 22, 2004 -- The Ion and Electron Spectrometer (IES), one of three NASA instruments aboard the European Space Agency (ESA) Rosetta comet orbiter, successfully underwent an intensive commissioning exercise that qualified it for operation during the next decade.

"IES will perform very high-resolution measurements of the solar wind and the comet's ionized gas environment with exceptionally low mass (1.1 kg) as compared to previous instruments of its type," says IES Principal Investigator Dr. Jim Burch, vice president of the Space Science and Engineering Division at Southwest Research Institute® (SwRI®). "We eagerly anticipate that IES and the other Rosetta instruments will contribute to great strides in our understanding of comets and the origin of the solar system."

The spectrometer is flying aboard Rosetta with another SwRI-developed instrument, the Alice ultraviolet imaging spectrometer, which successfully passed its checkout in April 2004. A lander and 14 other instruments complete the suite of science investigations flying aboard the first mission ever to orbit a comet. The target for Rosetta is Comet 67P/Churyumov-Gerasimenko, which was discovered by two Soviet astronomers in 1969.

Despite its small size, laboratory tests showed the spectrometer achieves sensitivity comparable to instruments weighing five times more. IES is designed to measure the solar wind, detect ions that are sputtered off the comet's nucleus, measure photoelectrons emitted from the surface and determine how ions are funneled into the comet's ion tail.

Funded by NASA for flight aboard Rosetta, IES will help determine how comets respond to bombardment by the solar wind. The orbiter will rendezvous with the comet near the orbit of Jupiter, where the comet will be like a frozen snowball with no atmosphere or tail. Rosetta will then continuously orbit the comet for three years as it moves closer to the Sun and develops an atmosphere (the coma), along with a dust tail and an ion tail. During the mission an excursion down the ion tail will take place, and the lander will be dropped off on the surface.

The Rosetta spacecraft launched in February 2004, and the mission is expected to end in 2015. Prior to reaching the comet, Rosetta will make close flybys of the Earth (twice), Mars and two asteroids, with IES contributing to the associated science investigations.

The Jet Propulsion Laboratory (JPL) manages the U.S. Rosetta project for NASA.

Editors: Images to support this story are available at

For more information, contact Maria Stothoff, Communications, (210) 522-3305, Southwest Research Institute, PO Drawer 28510, San Antonio, TX 78228-0510.

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