Weather Forecast Dips For Tuesday Shuttle Launch

CAPE CANAVERAL, Fla. - The weather outlook for NASA?s Tuesday launch of the shuttle Discovery has dipped slightly, with an increased risk of rain showers and thick clouds preventing the planned space shot.

?We are concerned about the weather for tomorrow?s launch,? said Kathy Winters, NASA?s shuttle weather officer, during a morning briefing here at the Kennedy Space Center.

Discovery now has a 40 percent chance of good weather, down from 60 percent, for its planned 11:38 a.m. EDT (1538 GMT) launch toward the International Space Station (ISS). Weather forecasts improve for subsequent launch opportunities on Wednesday and Thursday, Winters said.

Commanded by veteran shuttle flyer Pamela Melroy, Discovery?s seven-astronaut STS-120 crew will deliver a vital connecting node to the ISS, swap one station crewmember and relocate an old U.S. solar array during a 14-day mission.

So far, poor weather at Discovery?s Pad 39A launch site has only had a limited impact on liftoff preparations, said NASA test director Steve Payne.

Rain showers delayed efforts to load Discovery with the super-chilled liquid hydrogen and liquid oxygen that will power the orbiter?s three fuel cells during flight by about one hour on Sunday, but shuttle workers were able to make up the lost time once the weather subsided, Payne said.

?That wasn?t a big deal,? he added. ?We had contingency time built in just for that.?

Payne said launch preparations are back on schedule with plans to roll back the shroud-like Rotating Service Structure, which protects Discovery from weather, at 3:00 p.m. EDT (1900 GMT) today.

Shuttle workers will also load final cargo items inside Discovery?s middeck later today. They are slated to begin fueling the orbiter?s 15-story external tank with the 520,000 gallons of liquid hydrogen and liquid oxygen propellant that will feed Discovery?s three main engines during the nine-minute launch to space at about 2:13 a.m. EDT (0613 GMT), Payne said.

Engineers have added some modifications to Discovery?s fuel tank, including tweaking the design of plumbing line mounts and stripping cork-like insulation from some brackets, to avoid the type of debris-shedding that dinged the belly-mounted heat shield of the shuttle Endeavour during NASA?s STS-118 launch on Aug. 8.

Flight controllers have also cut about an hour from the launch countdown to decrease the amount of time in which ice can form on Discovery?s cryogenic propellant-filled fuel tank, mission managers have said.

Discovery?s STS-120 mission will mark NASA?s third of four shuttle flights dedicated to space station construction this year.

NASA will begin broadcasting Discovery?s STS-120 launch and mission operations live on NASA TV at 6:30 a.m. EDT (1030 GMT) on Tuesday. Click here for SPACE.com?s live launch coverage, mission updates and NASA TV feed.

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