News Column

Boulder researchers keyed up as spacecraft chases down comet

July 20, 2014

By Charlie Brennan, Daily Camera, Boulder, Colo.



July 20--Boulder's imprint in space will be strengthened even further next month as an instrument designed by the Southwest Research Institute plays a critical role on the first spacecraft to reach a comet and send a lander to its surface.

The European Space Agency's Rosetta, having launched in 2004, is due to reach the periodic comet 67P/Churyumov-Gerasimenko about 3:45 a.m. MDT on Aug. 6.

According to the European Space Agency, the mission marks the first time a spacecraft will orbit a comet's nucleus, it will be the first spacecraft to fly alongside a comet as it heads toward the inner solar system, and it will also be the first spacecraft to examine from close proximity how a frozen comet is transformed by the warmth of the sun.

Rosetta, which conducted a flyby of the Asteroid Steins in 2008 and the Asteroid Lutetia in 2010, carries a suite of 11 different instruments designed to probe the past and current life story of its target comet. Boulder-based SwRI's contribution to the instrumentation is an ultraviolet spectrograph dubbed Alice.

"I'm crazy excited," said Southwest's Joel Parker, deputy principal investigator on Alice. "It launched in 2004, so the spacecraft has been out there for 10 years, and it has taken this long for it to have flybys of Earth and Mars to get into an orbit that could reach and match the comet's orbit.

"We knew it was going to be exciting, of course, but there's nothing like being there. ... We can't bring the comet to a lab, so we're bringing the lab to the comet."

Alice is no larger than a shoebox, weighs less than 4 kilograms, draws on only 4 watts of power, but has 1,000 times the data-gathering capability of instruments flown a generation ago.

Alice's ability to see the ultraviolet range of light around the comet will enable scientists to read the unique fingerprints of atoms and molecules and measure gas and dust associated with the comet.

"That gas and dust is not only from the surface, but also comes from inside the comet," Parker said. "So by looking at what that gas and dust is made of -- for Alice it's mostly the gas -- that tells us what the inside of the comet is made of."

"The Rosetta investigation is designed to provide an unprecedented window into both the origin of comets and the way comets work," said SwRI's Alan Stern, principal investigator on Alice.

'C.S.I. Rosetta'

Alice will look particularly closely at what are known as noble gases, such as helium, neon and argon, which Parker said can be utilized by scientists as "thermometers."

"They will freeze and they will melt at very distinct temperatures. So by looking at those types of gases, and when they come out of the comet, and how much there is of one compared to another, that will tell us, for instance, what temperature the comet might have formed at, and that will tell us where in the solar system the comet may have formed four and a half billion years ago."

Alice is the only instrument on Rosetta provided by SwRI. But Alice, along with the other science payload, together forms what Parker calls "C.S.I. Rosetta."

"We're using all these different methods to study the clues that can tell us about something that happened a long time ago, somewhere else."

Rosetta, after charting a circuitous route across the solar system, crossing the asteroid belt and traveling into deep space, will enter orbit around the icy comet at a distance more than five times Earth's distance from the sun.

While Rosetta project scientists consider Aug. 6 its "arrival day" at the comet, the spacecraft will actually enter an orbit and continually grow to closer to the comet, to the point where it releases a landing craft, outfitted with 10 scientific instruments of its own, on Nov. 11. The lander will be set free at a point about 5 to 7 kilometers from the comet, to go to its surface.

"How long the lander lasts depends on several things, but the minimum expected time is on the order of several days, a week or less," Parker said. "It could potentially last several months. The things that could mark the end of the lander could be, for instance, if too much dust covers the solar panels, so it can't recharge."

Also, it will not be able to survive as the comet draws closer and closer to the sun, reaching its nearest point in August 2015.

But the deployment of the Rosetta lander won't by any means mark the end of the mission.

"It will basically escort the comet through at least December of 2015, possibly longer than that," Parker said. "The orbiter will continue to fly with the comet, we'll watch the comet turn on, and we'll watch it as it does its closest pass to the sun.

"And then, we'll watch the comet as it starts quieting down again. We've never watched a comet from this close. All the other comet missions have been flybys, like one-night stands. This is a long-term relationship."

Contact Camera Staff Writer Charlie Brennan at 303-473-1327 or brennanc@dailycamera.com.

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(c)2014 the Daily Camera (Boulder, Colo.)

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Source: Daily Camera (Boulder, CO)


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