Looking in to the past; a comet's tale!
- Deep Impact Spacecraft Ready for Mission
Jul 1, 5:28 PM (ET)
By ALICIA CHANG
PASADENA, Calif. (AP) - A NASA spacecraft was speedily closing in on its
target Friday, a comet scientists hope to smash open this weekend,
producing celestial fireworks for the Independence Day weekend.
But the real purpose is to study the comet's primordial core.
Mission scientists said the Deep Impact spacecraft was 1 1/2 million
miles away from Tempel 1, a pickle-shaped comet half the size of
"We're closing in very rapidly, but we're still very far away," said
Michael A'Hearn, an astronomer at the University of Maryland and
principal investigator of the $333 million project.
The cosmic fireworks will not be visible to the naked eye. But skygazers
with telescopes can view the collision 83 million miles up from parts of
the Western Hemisphere - in the United States, west of a line from
Chicago to Atlanta, around 2 a.m. EDT Monday if all goes as planned.
Launched from Cape Canaveral, Fla., Deep Impact began a six-month,
268-million-mile voyage Jan. 12 toward Tempel 1. If all goes well, it
will be the first time that scientists have ever peered into the heart
of a comet.
The collision will not significantly alter the comet's path around the
sun and scientists say the experiment poses no danger to Earth.
On Saturday, the spacecraft will spring free an 820-pound copper
"impactor," which will begin a 500,000-mile dive toward the sunlit side
of the comet. The impactor will have three chances to correct its flight
path to ensure a collision, which is expected around 1:52 a.m. EDT
As the comet races toward it at 23,000 mph, the camera-equipped probe
will shoot pictures as it awaits its fate.
Rick Grammier, project manager at NASA's Jet Propulsion Laboratory in
Pasadena, said both the spacecraft and the impactor were operating
normally Friday and he expects a successful mission.
Scientists expect the collision to blast a crater in the comet and hurl
the pristine subsurface material out from the pit. Comets are considered
remnants of the solar system's building blocks, and studying them could
provide clues to how the sun and planets formed 4 1/2 billion years ago.
The 1,300-pound flyby spacecraft, carrying two cameras and an infrared
spectrometer, will witness the impact from a distance of 5,000 miles.
After the impact, the spacecraft will approach the comet, flying 310
miles beneath it, to get images of the aftermath.
Last month, the Deep Impact spacecraft detected the comet nucleus for
the first time through a hazy cloud of dust and gas surrounding the icy
body. The images taken from 20 million miles away should help the
spacecraft zero in on its target.
Scientists also observed several short-lived outbursts of ice from
Tempel 1 that dramatically brightened the comet. Many comets experience
flare-ups although scientists are not exactly sure why. Grammier said
the outbursts should have little impact on the spacecraft and probe.
Looks like another good example for Todd to use in discussing
astronomical sights. By the time we see the evidence of the explosion
(if the explosive hits its mark and detonates), the explosion itself
will have been several hours old.
Will we see something that actually happened in the past, or something
NASA just arranged to fool us into thinking it happened?