CAPE CANAVERAL, Fla. - NASA hopes to begin hauling the space shuttle Atlantis off its launch pad as early as 8:00 a.m. EDT (1200 GMT) Tuesday to avoid the effects of Tropical Storm Ernesto.
"It's clear in our minds that we are rolling back per plan unless something really extraordinary happens," NASA launch director Michael Leinbach said during a morning briefing here at the Kennedy Space Center (KSC).
There are only two opportunities to stop rollback procedures - one Monday afternoon and another just before Atlantis is lifted of the launch pad - should Ernesto weaken or shift course dramatically.
"It's unfortunate that we're in this situation, but we are and we know how to deal with it," Leinbach said.
Tropical Storm Ernesto is in the Caribbean and approaching southeastern Cuba, where it is expected to weaken before again building up to a Category 1 hurricane bound for the south Florida coast. NASA launch controllers fear the storm could barrage Atlantis' launch pad with wind blowing in excess of 40 knots and plan to safeguard the shuttle in KSC's immense Vehicle Assembly Building (VAB).
NASA shuttle weather officer Kathy Winters said National Hurricane Center forecasts predict Ernesto could grow into a Category 3 storm by the time it reaches Florida.
Sustained winds of 40 knots are expected at Atlantis' Pad 39B launch site as early as 3:00 a.m. EDT (0700 GMT) Wednesday, with hurricane force winds expected later in the day, Winters said.
Leinbach said pad crews are removing the super-cold propellant that powers Atlantis' fuel cells from the orbiter's tanks. They will decide whether to disconnect systems controlling the explosive bolts aboard Atlantis' solid rocket boosters - the first window for stopping rollback - early this afternoon, he added.
Weather has consistently dogged the launch of Atlantis' planned STS-115 mission to deliver new solar arrays and trusses to the ISS and resume construction of the orbital laboratory. A Friday lightning strike to Pad 39B vehicle checks that delayed launch attempts on Sunday and Monday, with Ernesto forcing the Tuesday scrub.
NASA has not set a new launch date for Atlantis' 11-day mission but the shuttle can launch anytime through Sept. 7, when shuttle officials agreed to stand down so Russian space officials can launch a Soyuz spacecraft toward the ISS on Sept. 14.
If Ernesto weakens to the point Atlantis does not have to leave its launch pad, the shuttle could be primed for launch late this weekend, possibly by Sept. 3, NASA officials said.
"If we actually roll back...we can't get to a T-0 before Sept. 7," STS-115 Mission Management Team (MMT) chairman LeRoy Cain said during the briefing.
It would take eight days once Atlantis is returned to its launch pad, assuming no post-storm clean up or repairs at KSC are required, Leinbach added.
Cain spoke to Atlantis' STS-115 commander and NASA astronaut Brent Jett earlier today.
Jett reportedly said the his STS-115 astronaut crew would likely head back to Johnson Space Center for additional training in Houston should it become necessary to rollback the shuttle and evacuate aircraft from the Shuttle Landing Facility here at KSC.
Shuttle managers are still hoping to launch Atlantis during its current window, but are looking at other opportunities later this year.
"We have already started already looking at our options beyond September, if you will," Cain said. "By no means are we giving up on September, but it's just the way we do business."
NASA has set daylight restrictions to launch Atlantis and photograph its external tank in orbit in order to better gauge how fuel tank safety changes perform during flight. Under that rule, NASA could launch Atlantis through Sept. 13, but that would conflict with Russia's Soyuz launch, ISS crew change and landing schedules.
While Russian space officials could opt to delay the Soyuz flight, which will carry a new crew to the ISS, to Sept. 18 to allow NASA more time to launch Atlantis, they are reluctant to do so because it would push the landing of another Soyuz - carrying Expedition 13 astronauts Pavel Vinogradov and Jeffrey Williams currently aboard the ISS - into the dark predawn hours in the steppes of Central Asia's Kazakhstan.
The next lighted window to launch Atlantis runs from Oct. 20 through Nov. 15, though specific requirements can shave that opening down to just a few days or so, Cain said.
The most optimum time is a two-day period between Oct. 26-27, NASA has said.
"We are looking at both ends of that window," Cain said of October's prime launch window, adding that there numerous other non-storm related scenarios that could prevent a September space shot. "Those are the kinds of things that we're looking at just to be a step ahead of the game."
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