Deep Impact

NASA Projectile to Blast Through Comet's Skin

Scientist hope to learn about sources of life's chemicals 

DAVID PERLMAN / SF Chronicle 15dec04

Image from the 1902 movie by Georges Méliès, Le Voyage dans la lune [A Trip to the Moon] . See notes below article.

For the first time in the record of space exploration, scientists are preparing to blast a crater from the heart of a comet to reveal the contents of an object that — like Earth — has been orbiting the sun since the solar system formed some 4 1/2 billion years ago.

The satellite mission, set to be launched next month, is seeking to discover not only what comets are made of, but also more about how the solar system began — and what role countless comets may have played in seeding the early Earth with the chemicals needed for life to begin on its long evolutionary path toward the present.

Called Deep Impact, the satellite will fly more than 268 million miles across the solar system in the next six months to encounter a comet called Tempel 1, some 83 million miles from Earth, and aim a disc-shaped copper projectile directly into the oncoming comet's path.

The result, say the scientists leading the mission, will be a high- velocity collision at 22,800 mph that will expose the comet's interior and form an impact crater larger than a football field. The fiery eruption of material created by the impact will be clearly visible to an array of telescopes in orbit and on Earth.

Deep Impact team members briefed reporters on the mission Tuesday in Washington and by closed-circuit television to other reporters covering the day's sessions of the American Geophysical Union meeting at Moscone Center in San Francisco.

"Only the internal materials of comets are unchanged from the beginning of the solar system," said Michael F. A'Hearn, an astronomer at the University of Maryland and the NASA mission's principal investigator. "But we have no data on their interior, and that's what we're trying to solve."

Launch date for the mission is Jan. 12, and the satellite's yard-wide, 820-pound probe is to collide with the racing comet July 4.

Engineers have been testing every possible contingency that might delay the launch from the Kennedy Space Center in Florida, including the satellite's ability to aim its projectile precisely at the comet's nucleus, said project manager Richard Grammier of NASA's Jet Propulsion Laboratory in Pasadena. If the launch is delayed, the last possible launch date is Jan. 28.

"It's been test, test, test, and now we're good to go," and his team's confidence is so high that the satellite has less than a 1 percent chance of missing the comet when it aims its projectile at the target on impact day.

"We'll be capturing the whole thing on the most powerful camera ever to fly in deep space," A'Hearn said. The satellite itself holds a major telescope equipped with a high-resolution camera, while a smaller camera rides aboard the impacting projectile to snap images swiftly as long as possible.

The smaller camera "will most probably be sandblasted before the impact, and of course it will be totally destroyed in the crash itself," A'Hearn said.

From the material blasted out of the comet the mission's scientists hope to discover what the pristine materials are made of, determine the comet's density, and analyze its near-surface layers.

Astronomers directing three of NASA's "Great Observatories" now flying in orbit — the Hubble, Chandra and Spitzer telescopes — will train their sights on the unprecedented impact experiment, while all 12 observatories atop Mauna Kea in Hawaii will also be focused on the crash, according to Karen J. Meech of the University of Hawaii's Institute for Astronomy.

Around the world, both amateur and professional astronomers equipped with telescopes will also be observing the comet before and during the impact, she said, and many will continue their observations long after the crash to study changes in the chemical luminescence of the comet's long glowing tail.

One of the most intriguing puzzles that the Deep Impact mission seeks to solve is whether comets carry inside them the organic chemicals required by all living things. When Earth first formed, it was so heavily bombarded by asteroids and comets that it must have been totally dry and lifeless, scientists have determined from the geologic record. Many believe that later comets, with vast quantities of water ice and possibly the right chemicals, may well have seeded Earth with all the constituents of life during the planet's first few million years.

The Deep Impact mission will seek to learn whether that scenario is possible.

Rocket Trouble Stalls Launch of Deep Impact Mission 

JUSTIN RAY / Spaceflight Now 14dec04

A manufacturing error discovered in a part of the Boeing Delta 2 rocket to launch NASA's Deep Impact comet striker will force on-pad repairs, further delaying liftoff that must occur during an unflexible one-month window.

The mission was supposed to blast off December 30 from pad 17B at Cape Canaveral Air Force Station, Florida. But concerns with the spacecraft's software postponed the launch to January 8.

The latest problem, announced Tuesday, slips the target launch date to January 12 so workers can replace part of the Delta vehicle that will send Deep Impact on its six-month trek to Comet Tempel 1.

The probe must launch by January 28 in order to reach this comet, setting up a rendezvous July 4 when the mothership watches a small impactor collide with Tempel 1's icy heart at 23,000 mph. Scientists want to observe inside the stadium-sized crater formed by the impact to study the pristine materials buried in comets.

If Deep Impact misses its launch window — for whatever reason — the spacecraft would be grounded while the mission is re-planned and a new comet is selected, possibly Comet Schwassmann-Wachmann 3. But that comet has a smaller nucleus and dustier environment, making it a much less desirable target compared to Tempel 1, Deep Impact principal investigator Michael A'Hearn said.

"If we fail to make it off by the 28th, then we have to look at other possible targets. We've done some preliminary work," A'Hearn said. "There are other targets we can go to, we've looked at half a dozen different comets. Each of them is not as good as Tempel 1 in one way or another, which is why we do not want to delay the launch (past January)."

"I have every confidence that we are going to make it by the 28th. We are well positioned now," said Rick Grammier, NASA's Deep Impact project manager. "So I honestly cannot see that we wouldn't be ready to launch during the launch window that we still have remaining."

The first delay was ordered after concerns were raised during pre-flight software checks.

"We were looking through what we call our our parameter reviews, which is where we sit down with the engineers and go through all of the software parameters that we have to make sure they are all set appropriately. And during that review, which is why we do the review, we discovered there were a couple of parameters that were not set the way we expected them to be," Grammier explained.

"So as an extra precaution, I asked for a delay in the launch in order to give us time to go back and re-run some tests that we had already completed. We wanted to go back and make sure the interaction of turning those parameters on did not affect our fault responses that we had already tested and validated. So we needed the extra time to not only run a couple of additional tests but also to review the data from those tests.

"Recently, we had another delay due to some launch vehicle issues with an inter-ring. Again, in one of the extra checks that was being done, which is called the review of the engineering paperwork, the Boeing folks discovered that the interstage ring had not had an appropriate heat treatment on a portion of it. Thus, they called an engineering review board and determined that the best thing to do would be to change that piece of the launch vehicle out and replace it with one that had, in fact, done a full check and passed all of its paperwork."

NASA said a Boeing engineer reviewing an "as-built" drawing of the vehicle discovered the interstage had not been heat treated to a revised higher specification. The barrel-shaped interstage is seated atop the first stage and encloses the much of the second stage during the initial minutes of ascent.

Boeing has located a replacement piece and started preparing to perform the switch at pad 17B where the rocket is already assembled for launch. To accomplish the replacement, the rocket's second stage must be detached and removed from the launch pad on Wednesday. That gives access to the interstage for the adapter's removal Thursday. The new hardware should be installed Friday, followed by the return of the second stage on Saturday.

Despite the last-minute glitches that have postponed the launch, Grammier said he was pleased the problems were caught.

"I'm very positive on it because it shows that the checks we have implemented and put in place, actually that's why they are there. They are there to take one last look at things, make sure things are tip-top shape, and they did catch a couple of errors and that makes me feel confident that our system is working."

Deep Impact is undergoing its final testing and preps at the Astrotech facility near the Cape. It will be fueled next week. Delivery to the pad for mating atop the Delta 2 rocket is scheduled for January 3.

There will be two instants in time to launch January 12, separated by 40 minutes if weather or technical snags spoil the first shot. Liftoff will be possible at precisely 1:08:20 p.m. EST (1808:20 GMT) and 1:48:04 p.m. EST (1848:04 GMT).

"From central Florida to the surface of a comet in six months is almost instant gratification from a deep space mission viewpoint," Grammier said. "It is going to be an exciting mission, and we can all witness its culmination together as Deep Impact provides the planet with its first man-made celestial fireworks on our nation's birthday, July 4th."

"We will be capturing the whole thing on the most powerful camera to fly in deep space," A'Hearn added. "We know so little about the structure of cometary nuclei that we need exceptional equipment to ensure that we capture the event, whatever the details of the impact turn out to be."

"In the world of science, this is the astronomical equivalent of a 767 airliner running into a mosquito," said Don Yeomans, a Deep Impact mission scientist. "It simply will not appreciably modify the comet's orbital path. Comet Tempel 1 poses no threat to the Earth now or in the foreseeable future."

source: http://www.spaceflightnow.com/delta/d311/041214delay.html 15dec04

Comet Smasher's Launch Plan Announced

MAGGIE McKEE / New Scientist 15dec04

The first spacecraft designed to blast into a comet's icy heart is set to lift off in January 2005, mission managers announced on Tuesday.

NASA's Deep Impact mission is scheduled to launch from Florida's Cape Canaveral Air Force Station aboard a Delta II rocket sometime between 12 and 28 January. After a six-month journey, a pair of spacecraft will study the ice-and-rock heart - or nucleus - of Comet 9P/Tempel 1, which orbits the Sun between Mars and Jupiter.

The conjoined spacecraft will separate as they approach the comet's nucleus. One craft will smash right into it while the other vehicle flies by the comet, observing.

Comet nuclei are thought to reflect the original composition of the solar system. But only a handful have ever been seen as they approach the Sun - burning off obscuring clouds of dust and gas, called comas. And no spacecraft has yet touched a comet's surface.

Peeling away layers "We've learned a great deal from studying imagery of the surface," says Tom Morgan, programme scientist for the mission at NASA's headquarters in Washington, DC, US. "But what we don't have is direct knowledge of the interior of a comet's nucleus. Deep Impact will be the first mission to peel away these outer layers."

Getting under the surface is important because the outer layers are heated and altered every time the comet nears the Sun, says principal investigator Michael A'Hearn at the University of Maryland in College Park, US. The mission will help constrain models of how deeply the alteration penetrates.

And it will help answer why comets eventually stop releasing the gas that produces their bright comas. Astronomers do not know whether the phenomenon is due to the comets simply "running out of steam" or to the growth of a crust that prevents ice from escaping the surface.

Plan of attack The two spacecraft will separate near the comet's six-kilometre-wide nucleus. The mother ship, called the flyby spacecraft, will then release a 370-kilogram copper-studded "impactor" craft in front of the comet. On 4 July 2005, the comet will ram into the impactor at an estimated 37,000 kilometres per hour.

The impactor will be destroyed in the crash, but it will relay pictures of the comet until its very last electronic breath. These images will be the closest ever taken of a comet nucleus and could show details as small as 20 centimetres across.

The smash will blast away a crater that could be 14 stories deep and as wide as a football stadium. And it will eject debris that will cause the comet to brighten due to reflected sunlight. For about a day after the collision, the flyby spacecraft will snap visible and infrared images of both the debris and the crater to study their structure and composition.

All eyes watching But many more observatories will be watching too, recording the event at a range of wavelengths and over many days as the ejected dust dissipates and fades. The Hubble, Spitzer, and Chandra telescopes will observe from space, and a host of instruments, including all of the powerful telescopes on Hawaii's Mauna Kea, will observe from Earth.

Amateur observers between New Zealand and Arizona may be able to observe the actual impact with small telescopes - or even with the naked eye if the comet brightens enough.

Team members are quick to point out that the choreographed crash will hardly change the comet's orbit. "It's a fairly small crater in comparison to the nucleus," says Karen Meech at the University of Hawaii in Hilo. She adds that objects hit comets all the time, as evidenced by the craters seen in images of nuclei.

The $330 million mission will effectively end about a month after the collision, when the flyby spacecraft finishes sending all of its stored data back to Earth. It will then move into a safe solar orbit or, if NASA provides more funding, scout out a second comet.

source: http://www.newscientist.com/article.ns?id=dn6799 15dec04

NASA Set to Launch First Comet Impact Probe

PRESS RELEASE / NASA 14de04

Donald Savage Headquarters, Washington (Phone: 202/358-1547)
DC Agle Jet Propulsion Laboratory (JPL), Pasadena, Calif. (Phone: 818/393-9011)
George Diller Kennedy Space Center, Fla. (Phone: 321/867-2468)
RELEASE: 04-392

Launch and flight teams are in final preparations for the planned Jan. 12, 2005, liftoff from Cape Canaveral Air Force Station, Fla., of NASA's Deep Impact spacecraft. The mission is designed for a six-month, one-way, 431 million kilometer (268 million mile) voyage. Deep Impact will deploy a probe that essentially will be "run over" by the nucleus of comet Tempel 1 at approximately 37,000 kph (23,000 mph).

"From central Florida to the surface of a comet in six months is almost instant gratification from a deep space mission viewpoint," said Rick Grammier, Deep Impact project manager at NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif. "It is going to be an exciting mission, and we can all witness its culmination together as Deep Impact provides the planet with its first man-made celestial fireworks on our nation's birthday, July 4th," he said.

The fireworks will be courtesy of a 1-by-1-meter (39-by-39 inches) copper-fortified probe. It is designed to obliterate itself, as it excavates a crater possibly large enough to swallow the Roman Coliseum. Before, during and after the demise of this 372-kilogram (820-pound) impactor, a nearby spacecraft will be watching the 6-kilometer (3.7-mile) wide comet nucleus, collecting pictures and data of the event.

"We will be capturing the whole thing on the most powerful camera to fly in deep space," said University of Maryland astronomy professor Dr. Michael A'Hearn, Deep Impact's principal investigator. "We know so little about the structure of cometary nuclei that we need exceptional equipment to ensure that we capture the event, whatever the details of the impact turn out to be," he explained.

Imagery and other data from the Deep Impact cameras will be sent back to Earth through the antennas of the Deep Space Network. But they will not be the only eyes on the prize. NASA's Chandra, Hubble and Spitzer space telescopes will be observing from near-Earth space. Hundreds of miles below, professional and amateur astronomers on Earth will also be able to observe the material flying from the comet's newly formed crater.

Deep Impact will provide a glimpse beneath the surface of a comet, where material and debris from the solar system's formation remain relatively unchanged. Mission scientists are confident the project will answer basic questions about the formation of the solar system, by offering a better look at the nature and composition of the celestial travelers we call comets.

"Understanding conditions that lead to the formation of planets is a goal of NASA's mission of exploration," said Andy Dantzler, acting director of the Solar System division at NASA Headquarters, Washington. "Deep Impact is a bold, innovative and exciting mission which will attempt something never done before to try to uncover clues about our own origins."

With a closing speed of about 37,000 kph (23,000 mph), what of the washing machine-sized impactor and its mountain-sized quarry?

"In the world of science, this is the astronomical equivalent of a 767 airliner running into a mosquito," said Don Yeomans, a Deep Impact mission scientist at JPL. "It simply will not appreciably modify the comet's orbital path. Comet Tempel 1 poses no threat to the Earth now or in the foreseeable future," he added.

Ball Aerospace & Technologies in Boulder, Colo., built NASA's Deep Impact spacecraft. It was shipped to Florida Oct. 17 to begin final preparations for launch.

Principal Investigator A'Hearn leads the mission from the University of Maryland, College Park. JPL manages the Deep Impact project for the Science Mission Directorate at NASA Headquarters. Deep Impact is a mission in NASA's Discovery Program of moderately priced solar system exploration missions.

source: http://deepimpact.jpl.nasa.gov/press/041214nasahq.html 15dec04

Notes:

Georges Méliès. Le Voyage dans la lune [A Trip to the Moon]. 1902. 35mm film, black and white, silent, 11 minutes (approx.)

A Trip to the Moon is a satire in which the innate conservatism of the scientific community is overcome by the convictions of a lone charismatic figure (played by the filmmaker himself). This one-reel film spared no effect or expense in bringing to life Méliès's intensely personal vision. Astronauts prepare for a rocket-launching, take off, land on the moon (hitting it in the eye), and finally splash down back on earth.

Perhaps the greatest tribute paid to Méliès by his peers was the fact that, rather than attempting to duplicate the marvels contained in A Trip to the Moon, they simply stole it and released it under their own names, particularly in the United States. Méliès produced hundreds of films over the next decade. He had been a renowned magician and showman, who first became fascinated with projected images when he incorporated magic lanterns (early slide projectors) into his stage presentations at the Théâtre Robert-Houdin in Paris. Inspired by the work of the Lumière brothers, Méliès went on to build Europe's first true film studio, at Montreuil, and began to make films indoors in a stagelike space with artificial lighting. He produced action shorts, fictional tales, and spectacles; but he was most successful with his fantasy works, the most famous of which is A Trip to the Moon.

source: http://www.moma.org/collection/depts/film_media/blowups/film_media_002.html 15dec04

• For more still shots from the movie, see: Le Voyage dans la Lune [A Trip to the Moon] (1902)