The ,space shuttle Atlantis has a 70% chance of getting rained out,

Weather outlook Thursday's launch of the space shuttle Atlantis has a 70% chance of getting rained out, NASA mission managers said this morning.

A cold front moving across the U.S. this week unleashed dozens of tornadoes in the mid-South late Tuesday evening and continues to churn up thunderstorms. NASA doesn't expect a twister to botch their 2:45 p.m. ET launch opportunity on Thursday, but the threat of a thunderstorm, showers or thick cloud cover has lowered launch expectations from 40% to 30%.


Jeff Spaulding, NASA test director, said the best case scenario is if inclement conditions suddenly clear up before launch time.

"We always hope for that," Spaulding said. "As we all know, weather in Florida changes very rapidly. Things may improve or improve enough to get us the ability to get off the ground. The worst case would be if ... we'd have to try a different day."

Showers concern NASA because rain can damage the thermal protection shield of Atlantis during its high-speed launch. Heavy cloud cover is also problematic, Winters noted, because visibility of the shuttle as it launches can be obscured and pose a threat to public safety.

Should unfavorable conditions push the agency to scrub its launch in the early tomorrow morning, mission managers will aim for a 2:19 p.m. ET attempt on Friday. The chance of getting Atlantis into orbit then has also been lowered, from 40% to 20%, because of the potential for lingering rain showers.

As NASA crosses its fingers for a break in bad weather tomorrow, technicians continue to prepare Atlantis for its big moment.

The 100-ton orbiter's power-producing fuel cells have been filled and will be activated later this evening, following the retraction of launch Pad 39A's 13-story rotating service structure (RSS). The moveable scaffolding helps technicians service and inspect vital areas of the space shuttle after it is rolled out to the launch pad. Once the RSS is rolled back, it will reveal the freshly prepared Atlantis spacecraft.

The seven astronauts of the STS-122 mission have also been making final preparations for their space shot.

The 11-day mission, led by Navy captain Stephen Frick, is slated to deliver the European Space Agency's (ESA) 10.3-ton Columbus laboratory to the International Space Station (ISS). Pilot Alan Poindexter, mission specialists Leland Melvin, Rex Walheim and Stanley Love, and ESA astronauts Leopold Eyharts and Hans Schlegel will join Frick on the mission.

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Atlantis Waits On The Weather
Space shuttle Atlantis sits ready on launch pad 39A at the Kennedy Space Center in Cape Canaveral.
Not wind nor rain nor hail stops the U.S. Postal Service, but they do frustrate the people trying to launch space shuttles.

A weather front moving through Florida could put the brakes on Thursday's planned 2:47 p.m. liftoff of Atlantis, when storm clouds are expected to linger around Kennedy Space Center.

Air Force meteorologists give only a 30 percent chance of favorable conditions. If NASA begins pumping 500,000 gallons of fuel into the giant external tank about 5:30 a.m., the countdown will continue.

The seven astronauts were supposed to blast off in December on an 11-day mission to the International Space Station, but faulty fuel sensors forced lengthy troubleshooting and repairs on the pad. Now, with the shuttle given a clean bill of health, it's a matter of waiting out the weather.

If all goes well, Atlantis will take into orbit a giant science lab called Columbus, built by the European Space Agency. The 10-ton cylinder houses nearly a dozen science "racks" where astronauts will do experiments in near zero-gravity.

"Everything is ready to go," said Clare Mattok, a spokeswoman for the ESA. "Time really isn't a problem because we could wait on the pad until the end of March. This mission has been a long time coming, so a few extra weeks of delays won't make a difference."

But the National Aeronautics and Space Administration doesn't have as much wiggle room as it did in past years. The shuttle fleet is on target for retirement in 2010, and with less than a dozen missions left, the agency must complete as much of the space station as possible, and make repairs on the Hubble Space Telescope.

Atlantis' crew consists of commander Stephen Frick; pilot Alan Poindexter; mission specialists Leland Melvin, Rex Walheim and Stanley Love; and European Space Agency astronauts Hans Schlegel and Leopold Eyharts. Eyharts will remain on the space station, replacing Dan Tani, who will come home aboard Atlantis.