NASA Probe Will Collide With Comet Tempel 1 on July 4
28 June 2005
Deep Impact's encounter will unleash material dating to birth of universe
Washington -- After a voyage of 173 days and 431 million kilometers, a probe launched by NASA's Deep Impact spacecraft will collide with comet Tempel 1 on July 4 – a first-of-its-kind, hyper-speed impact between a space-borne iceberg and a copper-fortified probe.
NASA’s Deep Impact spacecraft and ground- and space-based observatories will record the potentially spectacular collision. Astronomers hope the collision will unleash primordial material trapped inside the comet, which formed billions of years ago.
"We are really threading the needle with this one," said Rick Grammier, Deep Impact project manager at NASA’s Jet Propulsion Laboratory (JPL) in California. "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."
Deep Impact will provide a glimpse beneath the surface of a comet, where material from the solar system's formation is relatively unchanged.
Mission scientists expect the project to answer basic questions about the formation of the solar system by offering the best view ever achieved of the nature and composition of the frozen celestial travelers called comets.
In the early morning hours (EDT) of July 3, the Deep Impact spacecraft will send a 1-meter-wide probe (called an impactor) into the path of the comet, which is about half the size of New York City's Manhattan Island.
Over the next 22 hours, Deep Impact navigators and mission members more than 133 million kilometers away at JPL will steer the spacecraft and impactor toward the comet. The impactor will head into the comet and the flyby craft will pass about 500 kilometers below.
Tempel 1 is hurtling through space at 37,100 kilometers per hour. Two hours before its collision with the comet, 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 crater produced by the impact could range in size from a large house to a football stadium, and from two to 14 stories deep. Ice and dust debris will be ejected from the crater, revealing the material beneath.
The flyby spacecraft will have 13 minutes to take images and scientific readings of the collision and the aftermath 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 Michael A'Hearn of the University of Maryland.
"With the information we receive after the impact, it will be a whole new ballgame,” he added. “We know so little about the structure of cometary nuclei [the permanent part of a comet] that almost every moment we expect to learn something new."
The Deep Impact spacecraft has four data collectors to observe the collision’s effects. The flyby spacecraft carries a High Resolution Instrument, composed of a camera and infrared spectrometer, and a Medium Resolution Instrument.
A duplicate of the Medium Resolution Instrument on the impactor will record the vehicle's final moments before it’s run over by Tempel 1.
"In the world of science, this is the astronomical equivalent of a 767 airliner running into a mosquito," said Deep Impact mission scientist Don Yeomans. "The impact ... will not appreciably modify the comet's orbital path. Comet Tempel 1 poses no threat to the Earth now or in the foreseeable future."
More information about Deep Impact is available at the NASA Web site, along with an encounter animation and an impact experiment video.
(Distributed by the Bureau of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)
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