Bullseye: Deep Impact Slams Into Comet
Impact ... deep impact: Image captured by Deep Impact's Flyby spacecraft of Impactor collision with Comet Tempel 1. Image
Credit: NASA/JPL.

This story was updated at 5:35 a.m. EDT.

PASADENA -- The Fourth of July began with a bang here early Monday morning as NASA's Deep Impact mission collided with history.

"There is a comet up in the sky wondering, what in the heck just happened," said JPL director Charles Elachi during a post-collision press conference.


This image shows the initial ejecta that resulted when NASA's Deep Impact probe collided with comet Tempel 1 at 10:52 p.m. Pacific time, July 3 (1:52 a.m. Eastern time, July 4). It was taken by the spacecraft's medium-resolution camera 16 seconds after impact. Credit: NASA/JPL-Caltech/UMD. Click to enlarge.

The $333 million mission to crash an 820-pound (371-kilogram) Impactor probe into the avocado-shaped Comet Tempel 1 and record the event via a Flyby mothership was a complete success. Mission managers at NASA's Jet Propulsion Laboratory (JPL) said the probe, jettisoned almost 24-hours earlier from Flyby, collided with the comet at 1:52 a.m. EDT (0552 GMT). The impact was confirmed by flight controllers on the ground at 1:57 a.m. EDT.

The control room erupted in cheers as the first images from Impactor's perilous approach to Tempel 1 were transmitted to Earth via the Flyby spacecraft.

"I can't believe they're paying us to have this much fun," exclaimed Don Yeomans, a Deep Impact mission co-investigator for JPL. "The impact was bigger than what I expected."

Deep Impact scientists said they have already received some data from orbital and ground-based observatories that provided additional vantage points to the impact.

"We're getting a lot of results," said Michael A'Hearn, Deep Impact principle scientist from the University of Maryland. "They observed a brightness increase of about two magnitudes, and a few telescopes reported big increases in the emission lines."

Good craftsmanship


The Hubble Space Telescope captured the Deep Impact collision with Comet Temple 1. Top is before the collision, the bottom image is after. Image Credit: HST

Impactor ended its almost six-month mission by successfully transmitting back images of the comet as it raced at a speed of 44,000 miles per hour into the surface of Tempel 1. That initial success, however was eclipsed when Flyby successfully transmitted back the first image of the Impactor's collision with Tempel 1.

"I just can't believe it. It's absolutely incredible," said Alice Phinney, Lead Mechanical Design Engineer for the Impactor at Ball Aerospace in Boulder, Colorado. She was one of over 600 company colleagues and friends that gathered at Boulder's Fiske Planetarium.

Phinney told SPACE.com that she worked on the Impactor that smashed into the comet for some two years. One of her key jobs was maximizing the use of copper in the Impactor design.

The task was not as straight-forward as it would seem. "There were a lot of assumptions. Scientists were all over the map," Phinney said regarding the overall composition of Comet Tempel 1.

"That's why I love engineering...at some point you've got to make a decision." The Impactor "worked like a champ," Phinney said.

Atop the Fiske Planetarium, rooftop observers using a 24-inch telescope reported seeing a brightness of the comet at impact.

"This is the biggest thing that's happened for the company," said Roz Brown, a spokeswoman for Ball Aerospace, which built the Deep Impact spacecraft. "This is huge for us."

Back to work


One of the first pictures of comet Tempel 1 from the Deep Impact mothership, as NASA scientists saw it. Credit: NASA/JPL. Click to enlarge.

After a brief celebration, Deep Impact flight controllers gradually called mission engineers and scientists back to their posts. Impactor's mission may now be finished, but its Flyby mothership still has images to deliver and more observations to make of Tempel 1's surface.

"We still have a Flyby spacecraft which is still collecting data, so we have to stay focused," JPL director Charles Elachi said. "I think it was worth every cent we spent on it."

The Deep Impact was reported as healthy after managing to track Impactor's collision with Tempel 1 down to about 50 meters, then turn its imaging lenses away from the comet to guard them from debris as the spacecraft passed underneath the nucleus.

In the two hours preceding the collision Impactor was basically on its own, as was the Flyby spaceship, Yeomans explained earlier in the day. Within that time period, Impactor performed three course corrections. Impactor's first targeting maneuver, or course correction, was a 21.5-second burn that occurred about 90 minutes prior to impact.

"As soon as the first [trajectory maneuver] went off on the Impactor and it worked fine the confidence just went sky high," Deep Impact's deputy project manager Kuyer Patel told SPACE.com. "We had a full spacecraft that had just been released on its own 24 hours ago and it had three sets of thrusters on it, one for attitude control and one for maneuvers. All of that got checked out right after its release so this was the only unknown left, so as soon  as that first trajectory change happened, everyone was just confident at that point."

The second course correction took place about 35 minutes prior to impact and the final at 12-and-a-half minutes.

"It takes 7/ ? minutes for the signal to get back to Earth, so you can't joystick this thing," Yeoman said. "You have to rely on the fact that the Impactor is a smart spacecraft as is the Flyby spacecraft. So you have to build in the intelligence ahead of time and let it do its thing."

Smooth autonomy


This image from NASA TV shows the nucleus of comet Tempel 1 from Deep Impact's flyby's high-resolution imager. Credit: NASA/JPL. Click to enlarge.

For mission managers, the spacecraft's automated controls worked perfectly. Such success will be repeated in the future, Yeomans said.

"This isn't the first time auto-navigation was used," Yeomans explained. "It was actually a back-up system for the Deep Space 1 mission that flew past Comet Borrelly back in 2001. That was a checkout for a back-up system that was not relied upon, but now, of course, we are indeed relying on it. So that's a new wrinkle for this mission."

Also, Deep Impact's use of optical navigation is something NASA has relied on for years.

"By using the onboard telescope system to prove our knowledge of where the comet is not new," said Yeomans. "But it builds on what has been done in the last several years in terms of 'smart' spacecraft. That is a trend, of course, to get this small army of navigators on the ground down to where it is now just a handful of folks."

Yeomans said he believed that it would take about 12 hours from impact to download all of the events images.

"But it will take months, even years, before all the science is even squeezed out of the data," said Yeomans. "Within the first six months the highlights will be published, but there will be analyses going on for quite some time. It's not just the spacecraft that is observing this comet. Chandra has observing in the X-ray spectrum. Spitzer will be observing in the infrared. Hubble will be observing in the visible."

Yeomans hoped that the success of Deep Impact would lead to more ambitious missions. "The next step is to actually rendezvous with a comet, orbit it, and then land and do surface analysis," Yoemans said. "Which is what the Europeans expect to do with the Rosetta spacecraft in 2014."

Ultimately, Yeomans said that the most ambitious mission would be to land on a comet, take a sample and return it for study in Earth-based laboratories. "There have been proposals to do just that. Nothing funded," Yoemans said. "But we're thinking that way."

SPACE.com Senior Space Writer Leonard David contributed to this story from Boulder, Colorado. Staff Writer Tariq Malik contributed to this story from New York City.

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