NASA's New Horizons Pluto Hours from Liftoff

The firstspacecraft ever aimed at the planet Pluto is hours away from launching intospace on a nine-year mission to the distant, icy world.

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A LockheedMartin-built Atlas 5 rocket is poised to launch NASA's Pluto-bound probe NewHorizons at 1:24 p.m. EST (1824 GMT) today from Complex 41 at CapeCanaveral Air Force Station in Cape Canaveral, Florida. If successful, today'sspace shot will begin a more than nine-year trek to Pluto and the Kuiper Beltfor the piano-sized spacecraft.

"This is avery exciting time," said Dale Cruikshank, a New Horizons science teamcollaborator with NASA's Ames Research Center, during Jan. 15 preflight briefing."We are poised to begin the exploration of a new world, a world we didn't evenknow that existed until 1930."

Discoveredby astronomer Clyde Tombaugh at Flagstaff Arizona's Lowell Observatory in 1930,Pluto is the only planet ever found by a U.S. citizen as well as the only onefound in the 20^th Century, NASA officials said.

NewHorizons' flyby mission will mark the first time a spacecraft from Earth hasvisited the small world, which will sit about three billion miles (nearly fivebillion kilometers) from our planet during the 2015 rendezvous. The spacecraftis also designed to visit one or more icy KuiperBelt Objects in an extended mission after the flyby.

Thespacecraft's launch window extends until about 3:23 p.m. EST (2023 GMT) today,though the probe can launch anytime before Feb. 14 of this year. If the probelaunches by Feb. 2, it will be able to snag a speed boost from Jupiter betweenFebruary and March 2007 and reach Pluto sometime in July 2015, NASA officialssaid.

NewHorizons and its Atlas 5 booster rolledout to the launch pad without a hitch Monday and appear on track for today'splanned launch.

Weatherofficials said Sunday that there is an 80 percent chance of favorable flight conditionsabove New Horizons' Cape Canaveral launch site, though they will be watching forhigh winds.

"We areexpecting winds in the lower 20 (knots) and mid-20s, and possibly gusts up to30 knots," said Joel Tumbiolo, the mission's launch weather officer from the 45^thWeather Squadron at the Air Force Station, during a preflight briefing. "All ofthose are below the threshold for our flight."

NASA willprovide live coverage of New Horizons' launch on NASA TV beginning at about11:00 a.m. EST (1600 GMT). You are invited to follow along using SPACE.com'sNASA TV feed by clicking hereor the link at the upper left of this page.

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