CAPE CANAVERAL, Fla.-NASA cleared the space shuttle Discovery and its seven-astronaut crew for flight Thursday as the clock ticks down towards a July 1 planned launch.
"We are ready to go for Saturday and do what NASA does best," said John Shannon, NASA's deputy shuttle chief and head of the STS-121 Mission Management Team (MMT), here at Kennedy Space Center.
Shannon said no major technical issues are afflicting the spacecraft or its launch stack, and that 21 top mission managers and engineers voted unanimously to forge ahead with Discovery's STS-121 mission-NASA's second shuttle flight since the 2003 Columbia accident-after a two-hour meeting.
Discovery's STS-121 mission will test new external tank safety modifications and deliver vital supplies to two astronauts currently circling Earth aboard the ISS.
But only if the weather will cooperate.
Weather officials said that the threat of isolated showers, thunderstorms and thick clouds, which could trigger lightning during Discovery's planned 3:48:37 p.m. EDT (1948:37 GMT) launch time, give the planned space shot a 60-percent chance of staying on Earth.
In fact, the lightning hazards prevented pad workers from loading Discovery with the liquid hydrogen and liquid oxygen fuels used to generate power during the spacecraft's 12-day mission to the International Space Station (ISS). The seven-hour operation was slated to begin at 1:00 p.m. EDT (1700 GMT) today, but launch officials were concerned that a lightning strike could ignite the super-chilled propellant in the event of a leak.
"We're a little bit behind schedule now," said NASA launch director Michael Leinbach. "We have plenty of hold time remaining in the countdown so right now I don't see this as a big issue."
Discovery's upcoming spaceflight will continue tests of shuttle heat shield inspection and repair techniques demonstrated during NASA's first post-Columbia flight-STS-114 aboard Discovery-last summer.
NASA's STS-121 astronaut crew, commanded by shuttle veteran Steven Lindsey, will also deliver European Space Agency (ESA) spaceflyer Thomas Reiter to the ISS, where he will join Expedition 13 crew of Pavel Vinogradov and Jeffrey Williams. Reiter's arrival will return the space station to its three-person capacity after more than two years of limited, two-person crews.
"ESA and indeed Europe is very proud to be part of what's going on at the moment," said Alan Thirkettle, ISS program manager for ESA. "We're very excited about the idea of one or our astronauts, Thomas Reiter, joining the space station crew for a six-month increment for the first time on ISS."
But first Discovery must leave Earth, a problematic endeavor if current forecasts-which predict a 60-percent chance of weather-related flight rule violations-continue throughout the first few days of the STS-121 launch window, which extends from July 1 through July 19.
"We're in good shape, we're just waiting for the weather to clear for us," Leinbach said.
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