The Ion and Electron Spectrometer (IES) and Alice ultraviolet imaging spectrometer, will analyze the dust and gases emanating from the surface of Comet 67P/Churyumov-Gerasimenko.

With these and other instruments, the Rosetta spacecraft will make the most thorough investigations of a comet ever attempted. Alice and IES were funded by NASA through a contract with the Jet Propulsion Laboratory as a part of the U.S. contribution to the ESA mission.

Both instruments were built with miniaturization of their electronic systems as a priority. IES was fabricated from magnesium to achieve a total mass of only 1,040 grams. Despite its small size, laboratory tests showed IES achieves sensitivity comparable to instruments weighing five times more.

The shoebox-sized Alice has one-third to one-half the mass of comparable UV spectrometers and yet has more than 10,000 times as many imaging pixels as did the UV spectrometer aboard NASA's Galileo Jupiter orbiter mission.

"The miniaturization of these instruments adds up to a considerable savings in cost, mass, volume and power," says Dr. James L. Burch, vice president of the SwRI Space Science and Engineering Division and IES principal investigator. "That makes them suitable for a variety of other interplanetary and Earth-orbiting satellite missions, as well."

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.

"We expect Alice to reveal new insights into the origin, composition and workings of comets -- insights that cannot be obtained by either ground-based or earth-orbital observations," says Dr. Alan Stern, principal investigator of the instrument and its scientific investigation. Alice will be the first UV spectrometer to study a comet up close. A sister instrument is also set to fly aboard the New Horizons mission to Pluto in January 2006.

IES and Alice both feature an advanced "micro-channel plate" detector, sophisticated optics and a miniaturized 6,000-volt power supply, and operate on just 3 watts, roughly 1/25 the power of an average light bulb.

"The Rosetta mission has to operate out to 5 AU (astronomical units), where the Sun is only 4 percent as bright as it is here on Earth. Because the spacecraft gathers its energy from the Sun using a large solar array, each instrument must do its part to be highly efficient," notes Alice Project Manager John Scherrer, a senior program manager at SwRI.

Following the launch, the spacecraft will make a 10-year journey to the comet and will make flybys of the Earth-moon system, Mars and at least one asteroid. In addition to making observations as it orbits the comet, the Rosetta Lander will carry a package of European instruments to the comet surface.

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