KENNEDY SPACE CENTER (AP) - The countdown has begun. NASA is now officially counting down the days and hours until the scheduled Tuesday morning launch of the space shuttle Discovery. But, there is an air of uncertainty.

Test director Pete Nickolenko says, despite a very thorough
troubleshooting analysis, they haven't gotten to the bottom of the
fuel-gauge problem that scrubbed the July 13th launch.

He says, "no doubt there is some degree of finger crossing." The seven-member crew is back at the Kennedy Space Center, after taking refresher training in Houston.

NASA's weather experts say there's a 60-percent likelihood that conditions will be fine for launch. This will be the first shuttle to go into space since the 2003 Columbia disaster.