Preparing for Deep Impact

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Deep Impact probe. Image Credit:NASA

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.

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The rocks inside a crater on the Asteroid Eros, as imaged before impact with the NEAR spacecraft. Numerous small impacts on the asteroid show brown boulders visible interior to the less exposed (white) lip of the crater. False-color for emphasis.
Image Credit: NASA/Eros

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.

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Comet Halley imaged by European flyby.
Credit: ESA

The Deep Impact spacecraft is designed to launch a copper projectile into the surface of comet Tempel 1 on July 4, 2005, when the comet is 133.6 million kilometers (83 million miles) from Earth. When this 372-kilogram (820-pound) "impactor" hits the surface of the comet at approximately 37,000 kilometers per hour (23,000 miles per hour), the 1-by-1 meter projectile (39-by-39 inches) will create a crater that could be as large as a football field.

Deep Impact’s "flyby" spacecraft will collect pictures and data of the event. It will send the data back to Earth through the antennas of the Deep Space Network. Professional and amateur astronomers on Earth will also be able to observe the material flying from the comet’s newly formed crater, adding to the data and images collected by the Deep Impact spacecraft and other telescopes. Tempel 1 poses no threat to Earth in the foreseeable future.

Past missions that have flown by a comet have been: NASA’s ICE mission in 1985, the two Russian Vega spacecraft and the two Japanese spacecraft Suisei and Sakigake that were part of the armada that visited Comet Halley in 1986; NASA’s Deep Space 1 flew by Comet Borelly in 2001 and NASA’s Stardust, which flew by Comet Wild 2 earlier in January and has captured samples of the comet’s coma to be returned in 2006. On Valentine’s Day, 2001, the Near-Shoemaker spacecraft successfully landed on the asteroid, Eros. Its remarkable journey–to soft-land on a peanut shaped asteroid - about 176 million kilometers (109 million miles) from Earth, prompted Andrew Cheng, NEAR Project Scientist, to note: "On Monday, 12 February 2001, the NEAR spacecraft touched down on asteroid Eros, after transmitting 69 close-up images of the surface during its final descent. Watching that event was the most exciting experience of my life."


Related Web Pages

Great Impact: Part I: The Benefits of Hard Bodies
Great Impact: Part II: Much Ado about Nothing?
Great Impact: Part III: The Large and the Small
Great Impact: Part IV: On A Collision Course with Earth
Great Impact: Part V: Encore
Harpooning a Comet
Comet Cruise Glimpses Earth
Extraterrestrial Capture
Reading Rosetta
Coma for Halley’s Comet
Impact Hazards Website
NASA/JPL Near Earth Object Program
IAU Minor Planet Center