发信人: ZZGR (闲逛), 信区: Aviation [删除]
标 题: European Spacecraft's Asteroid Flyby a Success
发信站: BBS 未名空间站 (Tue Sep 9 12:04:18 2008)
Despite Glitch, European Spacecraft's Asteroid Flyby a Success
By Peter B. de Selding
Space News Staff Writer
posted: 6 September 2008
9:31 am ET
PARIS - Europe's Rosetta comet-chaser satellite successfully detoured to
take a look at a rare type of asteroid Friday, getting a close-up view of
the diamond-shaped Steins asteroid, a gray, 3-mile (5-km) wide rock that
appears in images as a pock-marked with multiple craters that ultimately
will help determine its age.
The European Space Agency (ESA) probe's narrow-angle camera apparently
switched off as it closed in on the asteroid Steins, but the photo survey
was ultimately "a sideline" mission to the actual flyby and another camera
worked perfectly, ESA officials said in a post-flyby briefing early Saturday
at the agency's ESOC space operations center in Darmstadt, Germany.
"We were very conservative, perhaps too conservative," said Uwe Keller,
principal investigator for Rosetta's OSIRIS camera, adding that the tool was
put into safe mode and was not damaged.
"Steins looks like a diamond in the sky," Keller added.
The billion-dollar Rosetta satellite, carrying a small instrument package on
a lander that will attempt to land on a comet in 2014, came to within 500
miles (800 km) of Steins as it hurtled through space at about 223 million
miles (360 million km) from Earth.
Fifteen instruments were trained on Steins. Much of the data will be
delivered in the coming weeks, but Rosetta mission managers said Saturday
that they have already downloaded enough data to say the flyby was a success.
"This was a very big test of the waters" for Rosetta, which was launched in
March 2004, said David Soutwood, director of science and robotic exploration
at the European Space Agency (ESA). "Three hundred and sixty million
kilometers is not just down the street. It is the first big step toward our
grand exploration of asteroids and comets. They're small but important. Our
solar system grew out of things like this. "
One of the flyby's most challenging aspects of the flyby was what ESA
officials called a "flip" maneuver in which the satellite changed its
attitude by 180 degrees for a brief period during the approach.
Andrea Accomazzo, Rosetta spacecraft operations manager, said the maneuver,
and the brief exposure of the temperature-sensitive underside of Rosetta to
the sun, "stretched the limits" of what ground teams felt they could do to
accommodate scientists' desire to see Steins in full sunlight, from as close
a distance as possible.
Satellite operations managers and Rosetta scientists eventually agreed that
500 miles (800 km) was as close as the satellite would be allowed to Steins.
Mission managers hope that an analysis of the flyby data that will be
arriving in the next few weeks will permit them to estimate Steins' age, in
part from an examination of the many craters on its surface.
Rosetta's principal mission is to take a close examination, in 2014, of the
comet 67/P Churyumov-Gerasimenko, and ultimately to send its small Philae
lander to the comet's surface, where it will attempt to use a spear-like
system to attach itself to the comet. But before reaching the comet, Rosetta
is due to swing past another asteroid - the space rock Lutetia - in June
"It looks like a typical asteroid, but it is really fascinating how much we
can learn from just the images," ESA's Rosetta mission manager Gerhard
Schwehm said of Steins. "This is our first science highlight; we certainly
have a lot of promising science ahead of us. I'm already looking forward to
encountering our next diamond in the sky, the much bigger Lutetia."
2008，the year of the Phoenix
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