Two reports this weekend of the 'fireworks' display NASA has planned for us Sunday overnight/Monday morning.
NASA Readies Space Probe to Blast Comet By ALICIA CHANG, AP Science Writer
It's a space mission straight out of Hollywood -- launch a spacecraft268 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 the820-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:
======= 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 Tempel1 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 Tempel1 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:
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