Weather Looks Pristine for Saturday Shuttle Launch
At NASA's Kennedy Space Center in Florida, space shuttle Endeavour makes its final approach toward the fixed and rotating service structures on Launch Pad 39A, at left, on May 31, 2009. The shuttle is due to launch June 13 toward the ISS.
Credit: NASA/Kim Shiflett.

NASA has begun counting down to the planned Saturday morning launch of the space shuttle Endeavour and is expecting pristine weather conditions for blast off.

Endeavour and its crew of seven astronauts have a 90 percent chance of good weather when they attempt to launch from NASA?s Kennedy Space Center in Florida at 7:17 a.m. EDT (1117 GMT) on Saturday, mission managers said today. The clocks began counting down toward the launch earlier today.

?Right now, Endeavour?s in great shape,? said NASA test director Steve Payne in a televised status briefing. ?The launch countdown is proceeding nominally and the weather looks like it?s going to cooperate. We?re ready to go fly this mission.?

The potential for thick clouds over the launch site pose the only concern since they can trigger lightning when a shuttle blasts off, mission managers said.

Endeavour is poised to launch a marathon 16-day construction flight to deliver an experiment porch for the station?s Japanese-built Kibo laboratory, as well as other gear to International Space Station. Five challenging spacewalks and a host of tricky robotic arm operations using three different arms are planned during the mission.

Veteran shuttle astronaut Mark Polansky will command Endeavour?s STS-127 six-man, one-woman crew. The seven shuttle astronauts will boost the space station?s current six-man population to 13 people - the most ever at the orbiting laboratory - when they arrive.

?This one promises to be a very exciting mission,? Payne said.

NASA has a slim three-day window in which to launch Endeavour. Weather forecasts for Sunday and Monday are still favorable but dip slightly, giving the shuttle an 80 percent chance of good launch conditions, mission managers said.

If the shuttle does not lift off by June 15, NASA plans to stand down to allow a pair of unmanned lunar probes to launch toward the moon from the nearby Cape Canaveral Air Force Station, mission managers have said. If Endeavour cannot launch this month, NASA?s next chance to try again arises on July 11, when sunlight and heating conditions at the space station are more favorable.

Endeavour?s STS-127 mission to the space station is NASA?s third of up to five shuttle flights planned for this year.

SPACE.com will provide Moskowitz in Cape Canaveral, Fla., and Senior Editor Tariq Malik in New York. Click here for mission updates and a link to NASA TV.

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