CAPE CANAVERAL - NASA's preparations for its first space shuttle flight in more than two years are going well, with only three days remaining until the planned July 13 launch.

All but primed for flight, the space shuttle Discovery sits atop Launch Pad 39B at NASA's Kennedy Space Center (KSC) with its payload stowed for liftoff, launch officials said here today.

"Discovery itself is in excellent shape," NASA test director Jeff Spaulding said during a morning countdown status briefing. "The aft and mid-body of the vehicle have been closed up for flight."

Launch officials will be called to their stations today at 5:30 p.m. EDT (2130 GMT), and at 6:00 p.m. EDT (2200 GMT) the clock will begin counting off the days, hours and seconds leading up to Discovery's planned launch, Spaulding added.

Discovery's STS-114 mission is scheduled to lift off at 3:51 p.m. EDT (1951 GMT) on July 13, though launch officials have a 10-minute window to make the space shot. That window opens at about 3:45 p.m. EDT (1945 GMT) on launch day. NASA hopes to launch Discovery by July 31 at the latest.

The Discovery orbiter is the first of NASA's three remaining shuttles to launch since the 2003 loss of Columbia and its astronaut crew. Columbia was damaged during liftoff by launch debris, which pierced the orbiter's vital heat-resistant skin on the shuttle's left wing. The shuttle broke apart during reentry on Feb. 1, 2003, when hot atmospheric gases entered the hole caused by the launch debris.

NASA officials have spent the time since the accident redesigning shuttle external tanks to prevent launch debris like that which doomed Columbia. New orbital tools and procedures have also been developed to survey the health of shuttles in orbit. Discovery's flight will be NASA's first test of those new tools and procedures, and a vital resupply mission to the International Space Station (ISS).

"A lot has happened in the last two and a half years," Spaulding said. "Our focus...has shifted from one of recovery and investigation to one of redesign and improvement, to mission processing and now launch."

The outlook is promising for Discovery's July 13 launch, though there is a 30 percent chance that poor weather could prevent the space shot, said Kathy Winters, NASA's shuttle weather officer, said. Should Discovery not launch on July 13, the potential of a weather violation increases to 40 percent for the following days, she added.

Launch officials said Discovery could lift off up to three days after its initial launch target in the event of a scrub. Launch attempts could take place on July 13-14, and July 16, though the shuttle's external tank and other reactants will have to be serviced after that point, they added.

The 28,000-pound (12,700-kilograms) payload for Discovery's STS-114 space shot, however, can sit aboard the orbiter indefinitely. It could remain of the orbiter even if NASA misses a July launch entirely, and resorts to the next shuttle flight window that runs between Sept. 9-24, shuttle officials said.

"Our hardware is very insensitive to time," said Scott Higginbotham, NASA's payload manager for the STS-114 mission. "So we're content to sit and wait as long as it takes to get this mission started."

Discovery is hauling a fresh cargo module laden with new tools, food and other supplies - including a 600-pound (272-kilogram) gyroscope to be installed during the STS-114 flight - to the ISS.

"It sure does feel good to be back in the saddle again, it's been too long," Higginbotham said. "We're excited to get ... started with the assembly of the space station again."

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