Deep Impact scores direct hit
Mission to strike comet goes as planned
Daily Camera, July 4, 2005
PASADENA, Calif. - The universe now contains one less spacecraft, one more cometary crater, and many happy scientists and engineers.
Capping a mission that unfolded with a precision surprising to even the scientists and engineers leading it, the NASA Deep Impact spacecraft's impactor vaporized itself on schedule at 11:52 p.m. MDT.
Mission control confirmed the impactor had been hit by the comet five minutes later,
sparking cries of excitement as the high-resolution imager shot arrived. It depicted a massive cloud of ejecta and dust emanating from the comet's lower hemisphere.
Mission control was jubilant, complete with high-fives and fist-pumping among scientists who have spent years waiting for the moment to happen.
"That image says it all," said NASA scientist Don Yeomans. "We hit it right where we wanted to."
The actual strike took place more than seven minutes earlier. It took the news more than seven minutes to cross the 83 million miles separating the flyby spacecraft from home. The news arrived via the 70-meter ears of NASA's Deep Space Network antennas in California, Spain and Australia, in the form of images of the impact shot from a distance of 5,350 miles by the Deep Impact flyby spacecraft.
The first high-resolution images of the comet, which Yeomans said were already among the best ever taken from a comet, were released about 30 minutes before impact . They showed Tempel 1 to be shaped like a nine-mile-long avocado. Ten minutes to impact , the impactor adjusted its trajectory to strike a bright spot toward the bottom of the comet. The move would give Deep Impact 's flyby module, which would fly beneath, a better look at the action.
For Ball, which built the $333 million spacecraft for NASA, the success is the crowning achievement of an effort spanning 5½ years and involving hundreds of workers.
Charles Elachi, director of NASA's Jet Propulsion Laboratory, called the mission "one of the most daring and risky space missions that we have ever undertaken" in a press conference Sunday.
The Deep Impact team made it look easy. The journey's key moments appear to have played out "just like one of our simulations," as NASA's deputy project manager Keyur Patel put it early Sunday.
A day before impact , the impactor separated flawlessly from its flyby mother ship and ended up on a course within a kilometer of its intended target, still 500,000 miles away. It all but guaranteed a hit.
Monte Henderson, Ball's Deep Impact program manager, said mission control had expected to be up to 18 miles off target 90 minutes before impact . That was when the first of just before three trajectory-adjustment maneuvers were to commence, the last being 12 minutes before impact.
"Typically as engineers we don't get really excited," Henderson said. "But this is very exciting."
About 25 minutes before impact , the impactor was still within a kilometer of being on target.
Had things gone differently with impactor separation, options included smashing the entire bird into the comet for the benefit of the Hubble Space Telescope and five other orbiting observatories. In addition, more than 50 land-based telescopes, including the world's largest Keck 1 and 2 telescopes on Hawaii's Mauna Kea watched Scientists won't know if the encounter answers the mission's key scientific questions until Tuesday, and scientists will be analyzing the data for years, said Yeomans. Scientists suspect comets helped seed Earth and the inner solar system with water and organic molecules, and think the innards of Tempel 1 can tell them if they are correct or not.
The scientific process will be slowed by the need to sharpen the vision of the flyby spacecraft's best telescope on the ground, with software originally designed for the Hubble Space Telescope.
The mission's scientists have a betting pool going on the crater's size, said Mike A'Hearn, a University of Maryland professor and lead Deep Impact scientist. A stadium-sized, circular pit is the leading contender, although others have bet on everything from the comet absorbing the 820-pound impactor like a sugar cube in coffee to the comet blowing apart completely.
Deep Impact 's flyby module will photograph the receding comet for 2½ days after impact , and send data for the 30 days until the mission's end. But for Ball, the mission is nearly over.
"Tomorrow my career starts getting a whole lot more boring," said Thomas Bank, Ball Aerospace's mission systems engineer for Deep Impact.
© 2008 Todd Neff