Two reports this weekend of the 'fireworks' display NASA has planned
for us Sunday overnight/Monday morning.
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NASA Readies Space Probe to Blast Comet
By ALICIA CHANG, AP Science Writer
It's a space mission straight out of Hollywood -- launch a spacecraft
268 million miles so it can aim a barrel-sized probe toward a speeding
comet half the size of Manhattan and smash a hole in it.
But that's what NASA expects its Deep Impact mission to do this
weekend, with a goal of viewing the icy core of a comet that may hold
cosmic clues to how the sun and planets formed. It's not without
challenges. To ensure a bull's-eye hit -- and a spectacular
Independence Day fireworks display in space -- several things must
happen just right.
Around 2 a.m. EDT Sunday, the Deep Impact spacecraft must release the
820-pound copper "impactor" on course for a collision expected 24
hours later with the comet Tempel 1.
Scientists are confident they will be able to position the probe in
the onrushing comet's path, though that calls for precise maneuvers
that the probe must execute without help from mission control. Once on
auto-pilot, the probe has up to three chances before the collision to
fire its thrusters to adjust its flight path for a direct strike.
"To hit the nucleus of a comet is a little bit like a baseball player
trying to hit a knuckleball," said Dave Spencer, mission manager at
NASA's Jet Propulsion Laboratory in Pasadena, which is in charge of
the $333 million project.
Comets are blobs of ice and dust that orbit the sun and were born
about 4.5 billion years ago -- nearly the same time as the solar
system itself. When a cloud of gas and dust condensed to form the sun
and planets, comets formed from what was left over.
Scientists hope studying them will provide clues to how the solar
system formed.
Tempel 1, their specimen, is a pickle-shaped comet that travels in an
elliptical orbit between Mars and Jupiter.
After springing the probe, the mothership must slightly change course
and stake out a prime seat 5,000 miles from the collision, which is
expected around 1:52 a.m. EDT Monday.
The comet, hurtling through space at a relative speed of 23,000 mph,
will run over the probe with energy similar to exploding nearly 5 tons
of dynamite. All the while, a camera on the impactor will be shooting
pictures as it heads toward its doom, as will the mothership from
afar.
Little is known about comet anatomy, so it's unclear what exactly will
happen when Tempel 1 is hit. Scientists expect the collision to spray
a cone-shaped plume of debris into space. The resulting crater could
be anywhere from the size of a house to a football stadium, and be
between two and 14 stories deep.
"We still don't know what this comet holds in store for us," said Rick
Grammier, Deep Impact project manager.
Scientists will work feverishly to download data from the spacecraft
before it makes its closest approach to the comet less than 15 minutes
after impact. Their worry is that Deep Impact could be damaged by
flying debris, risking the valuable data. A trio of space telescopes -
the Hubble, Chandra X-ray Observatory and Spitzer Space Telescope -
and dozens of ground observatories will also view the collision and
aftermath.
So will amateur astronomers in the western United States and Latin
America, who should be able to view the impact through their own
telescopes. It will not be visible in the eastern United States and
upper Midwest.
Launched in mid-January from Cape Canaveral, Fla., Deep Impact sent
images of the comet's nucleus for the first time last month from a
distance of 20 million miles away.
It also witnessed two outbursts of ice from the comet -- not a major
concern to scientists who have plenty else to worry about.
On the Net:
Deep Impact mission: http://www.nasa.gov/deepimpact
Copyright 2005 The Associated Press.
======= The second report on the expected fireworks; will
you be watching it happen? ===========
NASA Releases Probe to Collide With Comet By ALICIA CHANG
PASADENA, Calif. - A NASA space probe was bearing down on its comet
target Sunday in a mission scientists hope will end with a cataclysmic
crash -- and new insights into the origins of the solar system.
The 820-pound copper probe was on course to intercept the comet Tempel
1 to smash a hole in it so scientists can get their first peek at the
heart of one of these icy celestial bodies.
Comets are the leftover building blocks of the solar system, which
formed when a giant cloud of gas and dust collapsed to create the sun
and planets. Because comets were born in the system's outer fringes,
their cores still possess some of the primordial ingredients and
studying them could yield clues to how the solar system formed 4.5
billion years ago.
The "impactor" probe separated from the Deep Impact spacecraft early
Sunday and began a 500,000-mile suicide dive toward the sunlit section
of Tempel 1, a pickle-shaped comet half the size of Manhattan and 83
million miles away from Earth.
Workers in the mission control room at NASA's Jet Propulsion
Laboratory in Pasadena erupted in applause shortly after the
separation.
"The release went very well," said project manager Rick
Grammier. "Half of the hurdles are over."
Meanwhile, the mothership fired its thrusters to slightly change
course and stake out a front-row seat 5,000 miles from the high-speed
collision, which is expected to occur at 1:52 a.m. EDT Monday.
The probe will switch to autopilot two hours before Monday's
encounter, relying on computer software and thrusters to steer itself
into the path of the onrushing comet. If the probe's maneuvers are
off, the comet could miss and the mission would fail.
As Tempel 1 closes in at a relative speed of 23,000 mph, the probe
should beam back unprecedented pictures of its target in near
real-time until it is run over.
If all goes to plan, the mothership will record the crash and
resulting crater with its high-resolution telescope. About 15 minutes
after impact, the craft will make its closest flyby of the comet
nucleus, approaching within 310 miles. Scientists expect it will be
bombarded with flying debris and will stop taking pictures, turning on
its dust shields for protection.
NASA's brigade of space-based observatories, including the Hubble
Space Telescope, Chandra X-ray Observatory and Spitzer Space
Telescope, also will be pointing toward the comet to record the
impact. Professional astronomers from dozens of observatories in 20
countries also will observe the crash.
Little is known about comet anatomy, so it's unclear what exactly will
happen when Tempel 1 is hit. Scientists expect the collision will
spray a cone-shaped plume of debris into space. The resulting crater
can range anywhere from the size of a large house to a football
stadium and be between two and 14 stories deep.
The probe's anticipated impact could cause the comet to shine brighter
than normal and sky-gazers may be able to see celestial fireworks with
a telescope in parts of the Western United States and Latin America.
Deep Impact blasted off in January from Cape Canaveral, Fla., for its
six-month, 268 million-mile journey. In what scientists say is a
coincidence, the spacecraft shares the same name as the 1998 movie
about a comet that hurtles toward Earth.
Discovered in 1867, Tempel 1 moves around the sun in an elliptical orbit
between Mars and Jupiter every six or so years.
In April, the 1,300-pound spacecraft took its first picture of Tempel
1 from 40 million miles away, revealing what amounts to a celestial
snowball. Last month, still 20 million miles away, scientists saw the
solid core of Tempel 1 for the first time.
On the Net:
Deep Impact mission: http://www.nasa.gov/deepimpact
Copyright 2005 The Associated Press.
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Lisa Minter (lisa_minter2001@yahoo.com)