NASA Sends Dawn To Space; Asteroid Program Canceled, Reinstated

By JOHN ARNOLD Journal Staff Writer

Dawn is coming after all for the two largest asteroids in the solar system.

A month ago, NASA canceled its Dawn space mission due to technical problems and cost overruns. But project scientists, including a team from Los Alamos National Laboratory’s International, Space and Response Division, learned last week that the unmanned spacecraft’s planned launch in 2007 was on again.

"Of course, we’re in shock. We were in shock when it was canceled, and we were pleasantly surprised when it was reinstated." said Tom Prettyman, a LANL technical staff member who has led Los Alamos’ work on the mission. "We are certainly just grateful we have the opportunity to go forward."

By studying the asteroids Ceres and Vesta, researchers hope to learn more about the formation and evolution of the solar system more than 4.5 billion years ago.

Ceres, discovered by Giuseppe Piazzi in 1801, is the largest asteroid in the solar system, measuring about 600 miles in diameter. Vesta, discovered in 1807 by Heinrich Wilhelm Matthus Olbers, is the brightest asteroid in the solar system but is about half the size of Ceres.

The two minor planets are part of the asteroid belt that orbits the sun between Mars and Jupiter. As the solar system formed, the gravitational forces from Jupiter’s large mass may have prevented the asteroid belt from accreting into a planet, according to Prettyman.

"What’s left (in the asteroid belt) is representative of that early time, when the planets just started to form," he said. "What’s left there are kind of planetary embryos."

Prettyman’s team developed a key spacecraft component called the Gamma Ray and Neutron Detector, or GRaND. The instrument suite will measure the composition of the two asteroids, which couldn’t be more different. Ceres is round and icy may hold subsurface water. Vesta is oddly shaped, rocky and dry.

"To have two completely different things like this orbiting pretty much the same distance from the sun, leads us to ask a bunch of questions about how the solar system was formed and how you can have this situation with the asteroid belt," said Andy Dantzler, the director of planetary science division at NASA headquarters in Washington, D.C.

Until last week, it appeared those questions wouldn’t be answered by Dawn. The mission has endured a turbulent developmental ride since it was approved in 2001. It was canceled in December 2003, reinstated in 2004 and canceled again on March 2, after $257 million had already been spent, according to a NASA news release.

Technical problems centered around the spacecraft’s design and the readiness of its ion propulsion system, according Dantzler. Dawn will be the first purely scientific mission to use ion thrusters, a futuristic propulsion system that is much more fuel efficient than traditional chemical rockets.

"So getting the ion propulsion system up and running in a way that’s reliable, that adds quite a bit of complexity," Dantzler said in a phone interview.

Dawn mission leaders at NASA’s Jet Propulsion Laboratory appealed the project’s cancellation, prompting NASA headquarters to review the technical and budget issues again. In a rare move, NASA reversed its decision last week.

"It looks like the technical issues are in hand, and we should be able to move forward with it," Dantzler said. NASA hopes to launch Dawn in summer 2007. The $446 million mission is projected to reach Vesta in 2011 and Ceres in 2015, marking the first time a spacecraft will orbit two planetary bodies on the same mission, according to NASA.