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Countdown to Impact




Impactor release: Sunday 2:07 a.m. EDT
Impact with comet: Monday 1:52 a.m. EDT
First post-impact photo: Monday 2:08 a.m. EDT

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The Mission




NASA's Deep Impact spacecraft will fire a projectile into the heart of Comet Tempel 1 to expose materials frozen inside the rocky snowball since the solar system formed four billion years ago.

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Mission engineering
Deep Impact mission officials provide an engineering overview of the spacecraft's daring attempt to fire a small probe into Comet Tempel 1. This briefing occurred July 1 at JPL. (41min 04sec file)

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Science conference
Scientists working on the Deep Impact mission give an update on research into Comet Tempel 1 and preview what they hope to learn with the July Fourth impact. This briefing occurred July 1 at JPL. (32min 29sec file)

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Launch of Deep Impact!
A Boeing Delta 2 rocket blasts off from Cape Canaveral carrying NASA's comet-smashing probe called Deep Impact. This extended clip follows the mission through second stage ignition and jettison of the rocket's nose cone. (5min 37sec file)
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Tower rollback
The mobile service tower is rolled back from the Boeing Delta 2 rocket, exposing the vehicle at launch pad 17B just before daybreak. (3min 21sec file)
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Rocket preps
Assembly of the Boeing Delta 2 rocket at launch pad 17B and mating of the Deep Impact spacecraft is presented in this video package with expert narration. (6min 12sec file)
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Spacecraft campaign
The pre-launch campaign of Deep Impact at Cape Canaveral is presented in this video package with expert narration by a spacecraft team member. (5min 32sec file)
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Comet science
On the eve of Deep Impact's launch, mission scientists hold a news conference at Kennedy Space Center to discuss the comet-smashing project. (35min 17sec file)

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Mission overview
Rick Grammier, NASA's Deep Impact project manager from the Jet Propulsion Laboratory, provides a detailed overview of the spacecraft and its mission. (4min 54sec file)
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Science preview
Deep Impact principal investigator Michael A'Hearn explains how the comet collision will occur and what scientists hope to learn. (7min 11sec file)
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Deep comet impact was a dust-up, not a gusher
HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS NEWS RELEASE
Posted: July 11, 2005

Smithsonian astronomers watched as the "Impactor" probe from NASA's Deep Impact spacecraft hit Comet Tempel 1 last week. They monitored the impact using the ground-based Submillimeter Array (SMA) in Hawaii and NASA's orbiting Submillimeter Wave Astronomy Satellite (SWAS). Results are still coming in, but so far the scientists report seeing only weak emission from water vapor and a host of other gases that were expected to erupt from the impact site. The most conspicuous feature of the blast was brightening due to sunlight scattered by the ejected dust.


An artist's concept shows SWAS' ringside seat for the comet impact on July 4. Artwork Credit: NASA, B. Scott Kahler, David Aguilar
 
"It's pretty clear that this event did not produce a gusher," said SWAS principal investigator Gary Melnick of the Harvard-Smithsonian Center for Astrophysics (CfA). "The more optimistic predictions for water output from the impact haven't materialized, at least not yet."

Astronomer Charlie Qi (CfA) expressed surprise at these results. He explained that short-period comets like Tempel 1 have been baked repeatedly by the sun during their passages through the inner solar system. The effects of that heat are estimated to extend more than three feet beneath the surface of the nucleus. But the Deep Impact indicates that these effects could be much deeper.

"Theories about the volatile layers below the surface of short-period comets are going to have to be revised," Qi said.

As seen from Earth, a comet typically displays a fuzzy round head and a glowing tail. Both the head and tail consist of gases and dust ejected from the comet's nucleus - a frozen chunk of rock and ice about half the size of Manhattan Island.

Five decades ago, Harvard astronomer Fred Whipple developed a model of comet nuclei as "dirty snowballs." He hypothesized that comets consist of mostly ice with some dirt and rock mixed in. Modern astronomers often refer to comets as "icy dirtballs" instead, reflecting the prevailing view that comets contain more dust and less ice than previously believed.

Deep Impact was intended to test these theories by excavating material from the comet's interior, giving scientists clues to its composition and structure. The mission succeeded admirably, pulverizing a section of the comet larger than a house and releasing tons of material into space.

SWAS operators were puzzled by the lack of increased water vapor from Tempel 1. Post-impact measurements showed the comet was releasing only about 550 pounds of water per second - an emission rate very similar to pre-impact values, and less than seen by SWAS during natural outbursts in the weeks before the impact.

SMA measurements corroborate the SWAS findings. Although the SMA wasn't tuned to frequencies of water emission, which are difficult to observe from the ground due to atmospheric water vapor, it watched for other chemicals such as hydrogen cyanide. SMA astronomers saw little increase in production of gases following the impact. Gas production rates remained so low that they could set only an upper limit on the total.

"All we needed was a factor of three boost from the impact to get a definite detection," said Qi. "We didn't see that."

Qi added that the comet might become more active over the following days and weeks. "We're still hoping for a big outgassing from the new active area created by Deep Impact. If we see any signs of that, we'll make more observations."

The researchers will continue their careful and detailed analysis in order to interpret the SMA and SWAS measurements and what they indicate about the comet's composition.

"The big picture will emerge once astronomers meld data from different observatories at different wavelengths," said Melnick.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

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Additional coverage for subscribers:
VIDEO: IMPACT MOVIES FROM MOTHERSHIP (NARRATED) PLAY
VIDEO: RIDE ALONG AS THE IMPACTOR SLAMS INTO TARGET PLAY
VIDEO: LEAD SCIENTISTS PRESENTS LATEST RESULTS PLAY
VIDEO: MONDAY'S AFTERNOON NEWS BRIEFING DIAL-UP | BROADBAND
AUDIO: LISTEN TO NEWS CONFERENCE MP3

VIDEO: DEEP IMPACT SMASHES INTO COMET PLAY
VIDEO: NARRATION OF IMPACTOR'S FINAL IMAGES PLAY
VIDEO: IMPACT PICTURES EXPLAINED BY COMET EXPERT PLAY
VIDEO: POST-IMPACT NEWS CONFERENCE DIAL-UP | BROADBAND
AUDIO: LISTEN TO POST-IMPACT NEWS CONFERENCE MP3

VIDEO: "DEEP IMPACT: THE MISSION" MOVIE PLAY
VIDEO: "DIGGING OUT THE SCIENCE" PLAY
VIDEO: RECAP OF IMPACTOR DEPLOY ACTIVITIES PLAY
VIDEO: PREVIEW OF THE ENCOUNTER TIMELINE PLAY
VIDEO: LEARN MORE ABOUT THE SPACECRAFT PLAY
VIDEO: SCIENCE DATA FROM COMET OUTBURSTS PLAY
VIDEO: SUNDAY MIDDAY STATUS REPORT DIAL-UP | BROADBAND 1 & 2
VIDEO: MISSION ENGINEERING BRIEFING DIAL-UP | BROADBAND
VIDEO: FRIDAY'S SCIENCE CONFERENCE DIAL-UP | BROADBAND
MORE: DEEP IMPACT VIDEO COLLECTION!
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