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. “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
http://www.swri.org/press/rosetta.htm.