CAPECANAVERAL, Fla. - NASA mission managers today cleared the space shuttle Atlantisfor its planned Wednesdayliftoff and agreed to make three consecutive launch attempts before thisweek is out.
"Everybody'sgo," shuttle launch integration manager LeRoy Cain, who is leading Atlantis'preflight Mission Management Team, told SPACE.com after a press briefinghere at NASA's Kennedy Space Center (KSC) spaceport.
Atlantis isprimed to launch its six-astronautcrew toward the InternationalSpace Station (ISS) at about 12:29 p.m. EDT (1629 GMT) on Sept. 6, withcurrent weatherforecasts predicting an 80 percent chance of favorable conditions. NASA'swindow to launch the shuttle's STS-115mission in daylight conditions, while avoiding conflicts with an upcomingRussian Soyuz spacecraft's launch to the ISS, closeson Sept. 8.
Missionmanagers agreed to make three launch attempts in as many days - something triedonly once before in NASA's 25-yearshuttle history - to boost Atlantis and its cargo of newsolar arrays and a pair of 17.5-ton trusses to the ISS. The mission marksthe first major addition to the station since the STS-113 mission aboardEndeavour in late2002.
NASA launchdirector Michael Leinbach said mission managers typically plan for four shuttleattempts in five days, a process that allows up to a 95 percent chanceof a successful space shot.
"So threein a row is probably in the low 90s," Leinbach said. "To a man, to a woman, therewere no disagreements at all about trying three in a row. We want to get thisvehicle into orbit."
Threeconsecutive attempts to launch NASA's STS-101 mission in April 2000 wereprevented by poor weather, which is not anticipated for Atlantis' STS-115mission. Clouds within 10 nautical miles of the launch site, and isolatedshowers within 20 nautical miles of KSC's Shuttle Landing Facility arecurrently the only threats to a Sept. 6 launch, shuttle weather officials said.
NASA hopesto launch Atlantis under optimum daylight conditions to evaluate how modificationsto the shuttle's external tank affect a series of icefrost ramps that are covered in foam insulation. Tank engineers aredrawing up new ice frost ramp modifications to curtail their amount of foaminsulation - a potential source of hazardous debris during launch - and areexpected to hit a final design near the end of this month.
Wayne Hale,NASA's shuttle program manager, said that studies are underway to decidewhether the lighted restrictions for Atlantis' launch could be lifted if the shuttlefails to lift off this week.
Atlantis'STS-115 mission was originally set to be the first spaceflight to launchwithout such restrictions since the 2003 Columbia accident, andcould launch in late September or early October if shuttle officials agree toset aside the imposed daylight rules, Hale added.
The next daylightopportunity to launch Atlantis is Oct. 26, NASA officials have said.
Anysubstantial delay of Atlantis' ISS construction mission would add pressure toadditional missions downstream to completethe orbital laboratory, Hale said, adding that it is imperative to resumestation assembly.
"I'mextremely excited to be here because this is the purpose for which we fly,"Hale said.
Atlantis' flightpreparations have been plagued by seasonal thunderstorms, a launchpad lightning strike and a tropical depression - formerly TropicalStorm Ernesto - which prevented the shuttle from rocketing spaceward last week.Shuttle engineers and mission managers have since worked around the clock to prepareAtlantis for launch before its lighted September window closed, though Leinbachassured that nothing has been left to chance during that effort.
"We did notcut any corners," Leinbach said. "We did not take any chance at all that, inthis turnaround process, we've missed anything."
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