Discovery Set For Launch

(CBS/AP)  A fuel sensor system on Discovery's external tank passed its first test early Tuesday as NASA began fueling the space shuttle for the first launch attempt since the doomed Columbia flight two and a half years ago.

NASA officials monitored the fuel sensor system on the gigantic external tank throughout the three-hour fueling process and planned to conduct two other tests to make sure the sensors functioned properly. A faulty reading of a sensor caused a scrub on July 13 as astronauts were boarding the spacecraft.

A few relatives of the fallen Columbia astronauts are on hand for Tuesday's launch attempt. The VIP list is topped by first lady Laura Bush and Florida Gov. Jeb Bush, her brother-in-law.

Discovery and its crew of seven are scheduled to blast off for the international space station at 10:39 a.m. EDT. The chance of storm clouds puts the odds of good launch weather at 60 percent.

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If the shuttle Discovery launches as planned today, CBS News will have live television coverage beginning at 10:30 a.m. ET. CBSNews.com will also have a live Webcast of the launch and preparations all morning.

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NASA has the paperwork ready to go in case the equipment trouble that scrubbed the July 13th launch reappears - a technical problem which still isn't fully understood. NASA managers now say they will go ahead with the July 26th launch even if just three of the four fuel sensors are working, a deviation from a rule instituted after the 1986 Challenger explosion.

Only two sensors are said to be needed to do the job. But ever since NASA's return to space in 1988 after the Challenger space shuttle explosion, the space agency has decreed that all four have to work to proceed with launch.

Monday, NASA Administrator Michael Griffin called the deviation "an acceptable risk."

"Actually, it's quite a low one," said Griffin.

"We have addressed everything we know on the shuttle that can go wrong that we have the technology to fix," Griffin said. "Some things simply are inherent to the design of the bird and cannot be made better without going and getting a new generation of spacecraft."

reports NASA managers, asked whether safety is taking a backseat to schedule pressure, insist their approach is based on sound engineering. The managers say that although the sensor problem remains an "unexplained anomaly," exhaustive testing has convinced them that the problem is not a generic safety-of-flight issue.

Wayne Hale, chairman of NASA's mission management team, put it like this: "I wake up every day and I ask myself are we pushing too hard, are we doing this thoroughly, have we done the right technical things, have we asked the right people, have we built the tests properly?

"I think we're all still struggling a little bit with the ghost of Columbia and therefore we want to make sure we do it right," Hale said Monday. "Based on the last ten days worth of effort, the huge number of people and the tremendous number of hours that have been spent in testing and analysis, I think we're coming to the right place."

CBS News Correspondent Barry Bagnato reports the moment Discovery does launch, cameras and sensors will begin searching the spacecraft for the type of damage that downed Columbia in February 2003.

"We'll do a detailed photo survey of the outside of the shuttle and then we'll quickly downlink the photos back to the ground," says space station astronaut John Phillips. If critical damage is detected - too serious to repair - Discovery's crew could theoretically escape to the space station to wait in safety until another shuttle was sent to retrieve them.

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