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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