NASA flight controllers now have an extra day to launch the shuttle Atlantis towards the International Space Station (ISS) this month as mission managers added Sept. 8 among possible dates for the planned liftoff, agency officials said Wednesday.

"We do have the option for the eighth, I can confirm that," NASA spokesperson Katherine Trinidad told SPACE.com.

On Tuesday, NASA launch integration manager LeRoy Cain said Atlantis' best bet for a potential liftoff ranged between Sept 6-7, the last two days in the shuttle's flight window. A launch pad lightning strike and subsequent checks, as well as what is now Tropical Depression Ernesto, have delayed the shuttle's launch from the Kennedy Space Center (KSC) in Florida.

The initial launch window for Atlantis' STS-115 mission to deliver new solar arrays and trusses to the station stretched from Aug. 27 to Sept. 13, but NASA agreed to a Sept. 7 cutoff date to avoid conflicts with a planned ISS crew swap mission aboard a Russian Soyuz vehicle.

Russia's Federal Space Agency plans to launch that Soyuz spacecraft on Sept. 14, with a fallback date of Sept. 18. NASA ISS managers were in discussions with their Russian counterparts on whether to use that Sept. 18 reserve date, which would put the Soyuz landing of the space station's current crew - Expedition 13 - before sunrise on Sept. 29.

U.S. and Russian ISS managers hoped to preserve a lighted landing for the Expedition 13 crew as a safety measure, but do have past experience with nighttime Soyuz returns, NASA ISS program manager Michael Sufferdini said in a Tuesday teleconference. Night landings are not preferred because they can hamper recovery efforts, which would be critical if the landing astronauts are in distress, Sufferdini said.

"If the shuttle Atlantis lifts off on September 6-8, the Soyuz will be launched on September 18," Nikolai Sevastyanov, president of the Russian aerospace firm RSC Energia that launches Soyuz and Progress spacecraft reporters Wednesday in Star City according to the Russian Interfax News Agency.

At KSC, shuttle managers and engineers have gone to great effort to make Atlantis' September launch window. Current NASA guidelines call for the shuttle launch under daylight conditions to allow cameras on the ground, in the air and aboard the spacecraft's launch stack to record the performance of external tank modifications.

The cutoff to launch Atlantis this month under optimum lighting conditions is Sept. 13.

On Tuesday, NASA shuttle managers first hauled Atlantis off its Pad 39B launch site to avoid high winds and severe weather from Tropical Storm Ernesto, then rolled the shuttle back to the pad as the tempest weakened.

Ernesto made landfall in southern Florida early Wednesday, and has weakened into a tropical depression, according to the National Hurricane Center.

A ride-out crew of about 200 NASA workers arrived at the Florida spaceport at about 4:00 a.m. EDT (0800 GMT) to watch over the site while Ernesto passes, NASA KSC spokesperson George Diller said in an update. Ernesto's center is expected to pass close to KSC, with the entire storm to blow by midnight, he added.

Peak winds at Atlantis' launch pad are expected to reach 55 knots, well below the 70 knot cap for a shuttle at Pad 39B, Diller said. Sustained winds are expected to reach between 40-45 knots, with some locations expected between six and eight inches of rain while others prepare for rainfall of three to four inches.

"KSC could be in a position for employees to return to work on Thursday," Diller said, adding that the decision to reopen the center depends on the result of post-storm safety inspections.

Shuttle officials have agreed to restart Atlantis' launch countdown from scratch, picking the count up at T minus three days. To make an initial Sept. 6 attempt, the countdown would have to resume Sunday to preserve at least three opportunities to launch Atlantis.

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