Space Shuttle Atlantis on Track for Thursday Launch
NASA's space shuttle Atlantis sits atop its Pad 39A launch site at the Kennedy Space Center, where astronauts are preparing for a Dec. 6, 2007 launch to the International Space Station.
Credit: NASA/Kim Shiflett.

CAPE CANAVERAL, Fla. - NASA?s shuttle Atlantis and a massive European laboratory are on track for their planned Thursday launch toward the International Space Station (ISS).

Atlantis? seven-astronaut crew is slated to liftoff from a seaside launch pad here at NASA?s Kennedy Space Center (KSC) spaceport at 4:31 p.m. EST (2131 GMT), with a 90 percent chance of pristine weather conditions.

?The vehicle is looking good and the weather is looking good, too,? said shuttle weather officer Kathy Winters, of the U.S. Air Force?s 45th Weather Squadron, in a morning briefing.

Commanded by veteran shuttle astronaut Stephen Frick, Atlantis? STS-122 crew will haul the European Space Agency?s (ESA) 13-ton Columbus lab to the ISS during a planned 11-day mission. Three spacewalks are on tap for the spaceflight, but NASA may extend the mission by two days to add fourth excursion to inspect a balky ISS solar array joint.

NASA test director Jeff Spaulding said shuttle workers detected a small leak in ground equipment late Wednesday after loading super-chilled liquid hydrogen into Atlantis? tanks, but the glitch is not expected to hinder plans for tomorrow?s launch.

?It?s on the ground side only,? Spaulding told reporters. ?It is not a vehicle issue at all.?

NASA space shuttles use liquid hydrogen and liquid oxygen reactants to power their three fuel cells during orbital flight.

Spaulding said engineers will spend the bulk of today testing Atlantis? communication systems and loading the final pieces of cargo into the shuttle?s middeck. A pair of experiments and some last-minute food items are on that list, he said.

Frick and his STS-122 crew, meanwhile, plan to visit Atlantis at the pad today as part of the prelaunch preparations, NASA officials said.

At 8:00 p.m. EST (0100 Dec. 6 GMT) tonight, pad workers are expected to retract the shroud-like Rotating Service Structure that protects Atlantis from weather at its Pad 39A launch site.

NASA has a slim window that closes on Dec. 13 in order to launch Atlantis to the ISS while the angles between the station?s solar arrays and the sun are favorable for docked operations. If weather foils Thursday?s launch attempt, NASA could try again as early as Friday at 4:09 p.m. EST (2109 GMT).

Winters said the weather outlook offers an 80 percent change of favorable launch conditions on Friday, but will dip to about 60 percent on Saturday.

Atlantis? STS-122 mission will mark NASA?s fourth shuttle flight of the year and the second to deliver a new pressurized module to the ISS.

NASA will broadcast Atlantis' STS-122 mission live on NASA TV. Click here for SPACE.com's shuttle mission coverage and NASA TV feed.

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