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NASA launches comet-smashing spacecraft
With a launch window only one second long, Deep Impact rocketed away at the designated moment on a six-month, 268-million-mile journey to Comet Tempel 1. It will be a one-way trip that NASA hopes will reach a cataclysmic end on the Fourth of July. "We are on our way," said an excited Michael A'Hearn of the University of Maryland, the mission's chief scientist. Minutes later, the spacecraft shot out of Earth's orbit and onto its collision course. "We'll be there July Fourth," NASA launch director Omar Baez said. The flight was barely under way when an overheating problem — considered slight and not at all damaging — was detected by the spacecraft itself. Onboard computer software put Deep Impact in a protective "sleep" mode that flight controllers expected to emerge from within 24 hours, via recovery commands. "We don't see it as a long-term threat by any means," said project manager Richard Grammier. The spacecraft is healthy, with the solar panel deployed and generating power, and the temperature increase in the propulsion-system heaters is slight and well within safety limits, he said. Scientists are counting on Deep Impact to carve out a crater in Comet Tempel 1 that could almost swallow the Roman Coliseum. It will be humans' first look into the heart of a comet, a celestial snowball still containing the original building blocks of the sun and the planets.
Because of the relative speed of the two objects at the moment of impact —
23,000 mph — no explosives are needed for the job. The force of the smashup will
be equivalent to 4 1/2 tons of TNT, creating a flash that just might be visible
in the dark sky by the naked eye in one spectacular Fourth of July fireworks
display.
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![In this photo released by NASA a Delta II rocket carrying the Deep Impact spacecraft lifts off from the Cape Canaveral, Fla. Air Force Station Wednesday, Jan. 12, 2005. Scientists are counting on Deep Impact to carve out July 4 a crater ranging in size anywhere from two to 14 stories deep, and perhaps 300 feet in diameter in Comet Tempel 1. It will be humanity's first look into the heart of a comet, a celestial snowball still preserving the original building blocks of the sun and the planets. [AP]](xin_040102130812898315172.jpg)
