This story was updated
at 4:45 p.m. EST.
NASA's once-canceled
Dawn mission to visit a pair of asteroids has been reinstated following a
mission review, space agency officials said Monday.
NASA
initially canceled the Dawn
mission, which calls for an ion-powered spacecraft to visit two large
asteroids, earlier this month only to reverse that decision, which drew ire and
opposition
from planetary scientists at this month's 37th Lunar and Planetary Science
Conference (LPSC).
After an
in-depth study of the cost overruns and technical challenges plaguing Dawn's
development, NASA officials concluded that the mission should proceed towards a
summer 2007 launch target.
"When you're
doing deep planetary missions....there are always pretty tall challenges," NASA
associate administrator Rex Geveden told reporters in a Monday teleconference. "And
it looks like Dawn is ready to take those on and beat them."
The
decision buoyed Dawn mission scientists, who had mourned the project's
cancellation earlier this month.
"This
mission goes up and down, but I'm happy," Dawn team member Lucy McFadden, of the
Department of Astronomy at the University of Maryland in College Park,
Maryland, told SPACE.com. "I want to
get to work and get this thing off the ground."
Dawn's new light
NASA first
approved the Dawn mission in 2001 as part of its low-cost Discovery
mission program.
The
spacecraft's novel ion propulsion system draws on technology demonstrated by
NASA's Deep
Space 1 probe, though Dawn would mark the agency's first science mission to
employ such an engine. Europe's SMART-1
probe currently circling the moon also uses ion propulsion.
"This is,
in fact, quite an ambitious mission," said Colleen Hartman, NASA's deputy
associate administrator for science mission directorate, during the
teleconference. "The things we're doing here are tough, they're not easy."
Dawn is
destined to rendezvous and orbit both Vesta and Ceres,
two of the largest asteroids in the Asteroid
Belt, in 2011 and 2015, respectively.
"Getting to
Ceres and Vesta will be opening up our eyes to new
worlds," McFadden said, adding that the large asteroids formed quickly in the
early Solar System and harbor many mysteries for scientists, including their
surface composition and features. "We just have the barest hint from maps that
we've derived from the Hubble Space Telescope
on their surface features."
During its
development, the cost Dawn's mission swelled from an initial $373 million to
$446 million due to technical challenges, NASA officials said. That cost
overrun – and a 14-month launch delay from its intended summer 2006 target –
prompted NASA's March 2 decision to scrap the mission, which came after $257
million had already been spent, the agency said.
An
additional $14 million would have been required to cancel the mission
completely, NASA said.
Off again, on again
Technical
challenges revolving around Dawn's propulsion system, xenon fuel tank and
thermal stresses – among others – contributed to its cancellation, NASA
officials said, adding that those concerns have since been addressed by
additional data.
"What we
had here was a very gut-wrenching decision," Hartman said. "And we're very
happy to be going forward."
But a
review process instituted by NASA chief Michael Griffin to evaluate the
cancellation of NASA space missions proved successful for Dawn's supporters.
"The
science mission directorate decided to terminate it, and the appeal [was] to
see if we continue to fund Dawn or go on with that termination," said Andrew
Dantzler, director of NASA's solar system division at the agency's Washington,
D.C. headquarters, during an interview last week.
NASA officials
said Monday that the process is likely not one that will occur often, adding
that Dawn has accrued about $5 million in additional costs since the agency ordered
mission managers and scientists to stand down
last fall when cancellation discussions began in earnest.
"We
revisited a number of technical and financial challenges and the work being
done to address them," NASA associate administrator Rex Geveden said in an
earlier statement. "Our review determined the project team has made substantive
progress...we have confidence the mission will succeed."
The funds
to save the project likely prevented other programs from moving ahead, Hartman added.
"These are
hard choices and sometimes future missions or current missions have to
sacrifice," Geveden added during the teleconference.
Meanwhile,
Dawn scientists and engineers have their work cut out for them before they can
launch the spacecraft toward its asteroid targets atop a Delta 2 rocket. About
half of the spacecraft's hardware, which includes support components and
science experiments, is complete, NASA officials said.
"I want to
get to both of them," McFadden said of Vesta and
Ceres. "I can't believe I have to wait until 2015."
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