The Alice ultraviolet imaging spectrometer,
one of three NASA instruments aboard the European Space Agency (ESA) Rosetta
comet orbiter, successfully passed its space checkout last month. The
checkout occurred approximately 20 million kilometers from Earth under radio
command and control, leading to textbook “first light” observations of the
interplanetary hydrogen and a nearby, bright comet called C/2002 T7
(LINEAR).

“Rosetta’s launch was bang on the mark, and the spacecraft is well on its
way to its target comet. During this journey, Rosetta will also explore the
atmosphere of Mars during a flyby in 2007 and two asteroids in later years,”
says Dr. Alan Stern, Alice principal investigator and director of the Space
Studies Department at Southwest Research Institute. “When Rosetta encounters
Churyumov-Gerasimenko, the ancient comet it is targeted to orbit in 2014,
the NASA-SwRI Alice instrument will become the first ultraviolet
spectrometer to ever reach a comet.”

“Alice will spend hundreds of days in cometary orbit, analyzing the
composition of Churyumov-Gerasimenko’s atmosphere, mapping its surface and
studying the properties of fine dust particles coming off the comet,” Stern
says. “This investigation will provide an unprecedented window into both the
origin of comets and the way comets work.”

“Alice is a highly miniaturized spectrometer with more than 1,000 times the
data-gathering capability of instruments flown a generation ago, and a
sensitivity for atmospheric measurements comparable to the Hubble Space
Telescope — yet it weighs less than 4 kg and draws just 3 watts of power,”
explains Alice Project Manager John Scherrer, also of SwRI. “The successful
turn on and checkout of Alice in space represents a major milestone in the
U.S. Rosetta program.”

Alice Operations Scientist and SwRI Manager Dr. Joel Parker continues, “We
really couldn’t have expected a healthier instrument than we have. All
subsystems are performing nominally, and every indication we have is that
the instrument’s scientific performance is on spec.”

Alice was built and is operated by SwRI for NASA. The instrument is designed
to probe the atmosphere and surface of Churyumov-Gerasimenko. A sister Alice
instrument is also set to launch aboard the New Horizons mission to Pluto in
January 2006 for studies of that distant world’s atmosphere.

SwRI also built and will operate the Ion and Electron Spectrometer (IES)
flying aboard Rosetta. Principal Investigator Dr. James Burch, vice
president of the SwRI Space Science and Engineering Division, leads IES
operations. Despite its mass of just 1.04 kilograms, laboratory tests showed
the spectrometer achieves sensitivity comparable to other instruments
weighing five times more. IES will simultaneously measure the flux of
electrons and ions surrounding the comet over an energy range extending from
the lower limits of detectability, near 1 electron volt, up to 22,000
electron volts. It uses a novel, electrostatic scanning technique to view
particles from directions encompassing 70 percent of the celestial sphere.
Although not yet fully operational, preliminary tests of IES show it too is
operating nominally.

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

Editors: The Rosetta mission website is at
http://www.esa.int/SPECIALS/Rosetta/, and the Alice instrument website is at
http://www.esa.int/SPECIALS/Rosetta/SEMRHF374OD_0.html. Visit the New
Horizons website at http://pluto.jhuapl.edu. Additional images to support
this story are available from http://www.swri.org/press/rosetta.htm.