NASA officials, who had been keeping a wary eye on Hurricane Dennis, which was poised to slam into southwestern Florida, said Sunday that the menacing storm appeared to not threaten the launch area and likely keep other unfriendly weather at bay.

"You can thank Dennis slightly for the ridge moving to the north," said Kathy Winters, the shuttle's weather officer, who said current forecasts predict a 70 percent likelihood of clear weather at launch time.

The seven member Discovery crew late Saturday had arrived 24 hours earlier than originally planned to the launch site at the Kennedy Space Center in anticipation of weather-related problems, but those seem unlikely to materialize, US space officials said.

NASA has also been keeping a close eye on the weather system, but decided to go ahead with plans for Wednesday's launch of the space shuttle Discovery from Florida's Kennedy Space Center, which lies well clear of the hurricane's path.

It will be the first launch since the Columbia shuttle disaster grounded flights in February 2003.

An investigation into the February 2003 Columbia tragedy blamed more than just technical problems for the crash which resulted in the deaths of seven astronauts.

The Columbia Accident Investigation Board also faulted NASA culture, saying the space agency's managers were "as much a cause" of the crash as technical failures.

The National Aeronautics and Space Agency has taken steps to reform and it has made changes to the shuttle to minimize the risks of space flight as much as possible.

NASA says it has changed its structure to take into account the diverging opinions of engineers and technicians, voices that were previously ignored by agency managers.

Several technical changes were made to the Discovery shuttle to ensure a safe flight.

Loose insulating foam from an external fuel tank damaged Columbia's left wing on take-off, leading to the ship's dramatic breakup on reentry 16 days later, on February 1, 2003, and the death of its seven crewmembers.

For Discovery's mission, NASA modified the fuel tank's insulation to make potential debris so small that it would not cause any damage. The new fuel tank also has a heating system to reduce the risk of ice formation.

The new safety measures will also allow astronauts to check the Discovery shuttle's exterior while in space.

"The main way to get smarter about this problem is to go fly," said shuttle systems engineering manager John Muratore.

NASA has also installed new cameras on the shuttle and around the launch pad at the Kennedy Space Center near Cape Canaveral to keep a close eye on the launch until the orbiter separates from the main fuel tank eight minutes after take-off.

For a better view, NASA decided against launching at night, a move that reduces the number of opportunities to launch toward the International Space Station , which astronauts will continue building.

If damage is detected in orbit, two astronauts will be able to go on a space walk with new tools enabling them to fix Discovery. Three space walks are scheduled for the 12-day mission.

In one of the sorties, Japanese astronaut Soichi Noguchi and his American counterpart Stephen Robinson will go into space to test repair techniques that work back on Earth but are untested in orbit.

A Canadian-built tool that doubles the length of the shuttle's robot arm will allow astronauts to check for damage. Cameras and a laser system at its extremity will allow a millimeter by millimeter analysis of the shuttle's exterior.

The ISS crew will also assist in the inspection by photographing the shuttle's underside shortly before its rendezvous with the space station.

"If we get in a situation we cannot fix, we have the option to rescue the crew," said shuttle program deputy manager Wayne Hale.

Discovery would remain docked to the ISS while a rescue spacecraft is launched.

"We believe we have significant risk reduction," Hale said.

But he acknowledged that space travel remains inherently dangerous.

"We are still going to fly with some risk," Hale said.

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