[meteorite-list] NASA Announces Spectacular Day of the Comet (Deep Impact)

[Ron Baalke]

Dolores Beasley
Headquarters, Washington                              June 9, 2005
(Phone: 202/358-1753/1237)

D.C. Agle
Jet Propulsion Laboratory (JPL), Pasadena, Calif.
(Phone: 818/393-9011

RELEASE: 05-144

NASA ANNOUNCES SPECTACULAR DAY OF THE COMET

After a voyage of 173 days and 268 million miles, NASA's Deep 
Impact spacecraft will get up-close-and-personal with comet 
Tempel 1 on July 4.

The first of its kind, hyper-speed impact between space-borne 
iceberg and copper-fortified probe is scheduled for approximately 
1:52 a.m. EDT on Independence Day. The potentially spectacular 
collision will be observed by the Deep Impact spacecraft, ground 
and space-based observatories.

"We are really threading the needle with this one," said Rick 
Grammier, Deep Impact project manager at JPL. "In our quest of a 
great scientific payoff, we are attempting something never done 
before at speeds and distances that are truly out of this world." 

During the early morning hours of July 3, the Deep Impact 
spacecraft will deploy a 39-inch cubic shaped impactor into the 
path of the comet, which is about one-half the size of Manhattan 
Island, N.Y. Over the next 22 hours, Deep Impact navigators and 
mission members, more than 83 million miles away at JPL, will 
steer both craft towards the comet. 

The impactor will steer into the comet and the flyby craft will 
pass approximately 310 miles below. Tempel 1 is hurtling through 
space at approximately 6.3 miles per second. At that speed you 
could travel from New York to Los Angeles in less than 6.5 
minutes. Two hours before impact, when mission events will be 
happening so fast and so far away, the impactor will kick into 
autonomous navigation mode. It must perform its own navigational 
solutions and thruster firings to make contact with the comet.

"The autonav is like we have a little astronaut on board," 
Grammier said. "It has to navigate and fire thrusters three 
times to steer the wine cask-sized impactor into the 
mountain-sized comet nucleus closing at 23,000 miles per hour." 

The crater produced by the impact could range in size from a 
large house up to a football stadium from two to 14 stories 
deep. Ice and dust debris will be ejected from the crater, 
revealing the material beneath. The flyby spacecraft has 
approximately 13 minutes to take images and spectra of the 
collision and its result before it must endure a potential 
blizzard of particles from the nucleus of the comet.

"The last 24 hours of the impactor's life should provide the 
most spectacular data in the history of cometary science," 
said Deep Impact Principal Investigator Dr. Michael A'Hearn 
of the University of Maryland, College Park. "With the 
information we receive after the impact, it will be a whole 
new ballgame. We know so little about the structure of 
cometary nuclei that almost every moment we expect to learn 
something new."

The Deep Impact spacecraft has four data collectors to 
observe the effects of the collision. A camera and infrared 
spectrometer, which comprise the High Resolution Instrument, 
are carried on the flyby spacecraft, along with a Medium 
Resolution Instrument. A duplicate of the Medium Resolution 
Instrument on the impactor will record the vehicle's final 
moments before it is run over by Tempel 1.

"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. "The impact 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." 

Deep Impact will provide a glimpse beneath the surface of a 
comet, where material from the solar system's formation 
remains relatively unchanged. Mission scientists expect 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 frozen celestial travelers we call 
comets.

The University of Maryland is responsible for overall Deep 
Impact mission management, and project management is handled 
by JPL. The spacecraft was built for NASA by Ball Aerospace 
& Technologies Corporation, Boulder, Colo.

For more information about Deep Impact on the Internet, visit:

http://www.nasa.gov/deepimpact

For information about NASA and agency programs on the Internet, 
visit:

http://www.nasa.gov/home/index.html


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