[meteorite-list] NASA's Dawn Asteroid Mission Cancelled

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Mar 3 15:50:51 2006
Message-ID: <200603032049.k23Kn5Y09955_at_zagami.jpl.nasa.gov>

http://www.space.com/news/060303_dawn_cancelled.html

NASA's Dawn Asteroid Mission Cancelled
By Leonard David
space.com
03 March 2006

A NASA mission being readied for launch and designed to explore two
large asteroids in the solar system has been officially cancelled.

"We made the decision yesterday to cancel Dawn,' said Andrew Dantzler,
director of NASA's solar system division in Washington, D.C.

Dantzler told SPACE.com that NASA is looking at distributing Dawn
hardware to other missions currently being considered or in the future.
"Some of the subsystems should be good for other spacecraft," he said.

The Dawn spacecraft was to utilize an ion engine system, making use of
xenon gas. A slow-but-steady acceleration is created via an ionized
propellant stream. Ion propulsion relies on interactions of external and
internal magnetic fields with electric currents driven through the
stream, thereby imparting thrust to a spacecraft on which is it mounted.

Making use of its ion engine, Dawn was to reach 4 Vesta in 2011 and 1
Ceres in 2015. These objects are the two most massive asteroids known,
yet are very different from each other. Scientists had hoped by studying
the asteroids they would glean clues about the formation of the solar
system.

As a NASA Discovery-class mission, Dawn was selected in December
2001 - one of NASA's corps of spacecraft that are developed on a
fast-paced schedule and at modest cost compared to so-called "flagship"
missions.

Dawn was managed by the Jet Propulsion Laboratory (JPL) in Pasadena,
California with Orbital Sciences Corporation of Dulles, Virginia
developing the spacecraft.

The mission had been on NASA's books for liftoff in mid-June 2006, but
late last year was placed in "stand down" mode. Technical issues and
cost-growth in the project led to the decision, with an independent team
assigned the duty to look into the problems.

Assessment team findings

Last year it was becoming clear that there were issues with Dawn,
Dantzler explained. "The path for resolving all the technical issues and
the certainty on the cost number were not clear," he said.

The independent assessment team for Dawn was pulled together to dig in
and take at look at mission issues "and what it would take to get Dawn
to be ready."

That team reported to NASA in January that there were 29 individual
major issues that needed to be dealt with before Dawn was ready to go,
Dantzler said. Also, there was an increased cost growth of 20 percent
over Dawn's confirmation cost cap of $373 million, he added, as well as
a 14-month or more delay in launch.

"Over the past month or so we've been deliberating over those findings,"
Dantzler said, leading to yesterday's decision. Canceling Dawn was "the
fiscally responsible thing to do," he said, "...and at some point you just
have to draw the line."

NASA reached a point where it was not clear how long and how much money
it would take to get Dawn off the ground, Dantzler said. The space
agency is looking at a close-out cost-handling such things as hardware
storage and close-out paperwork - of somewhere between $9 million to $12
million, he said.

"This is clearly a tough decision. We don't take it lightly at all. But,
ultimately, I believe it's the right one for the good of the Discovery
program," Dantzler said.

Among the technical problems encountered, "there were still serious
concerns" about the readiness of the ion engine propulsion system for
Dawn, Dantzler said.

Asteroid frontier

When word came last year of the stand down, Dawn's principal
investigator, Christopher Russell of the University of California, Los
Angeles (UCLA) told SPACE.com that the mission could tolerate a later
launch date - without any science impact. He remained hopeful that NASA
would allow the mission to proceed to launch.

"I am having a difficult time processing and accepting the
cancellation," said Lucy McFadden of the Department of Astronomy at the
University of Maryland in College Park, Maryland and a Dawn team member.

"With the success of the Discovery Program's Deep Impact and Stardust
missions, and the recent and exciting scientific results from the Hubble
Space Telescope on Ceres - we were poised to emerge into the asteroid
frontier with the Dawn spacecraft," McFadden told SPACE.com.

McFadden said that scientists can better understand asteroids as true
protoplanets, "if we could only send the spacecraft there." Furthermore,
there are equally intriguing clues to the intricacy of Vesta, a very
different asteroid that was also on Dawn's trajectory, she explained.

'There are hundreds of people in this country and in Europe who have
worked on the [Dawn] project for four years and had committed another
decade to it - and now we are dropped," McFadden said. "What can I say? It
makes me cry."
Received on Fri 03 Mar 2006 03:49:05 PM PST