NASA hopes it has fixed a fuel gauge problem as it prepares to launch the space shuttle Discovery on Tuesday.

Space agency managers say if the sensor problem pops up again during the shuttle's fueling, they may bend their own safety rules and launch anyway.

Liftoff is scheduled for 10:39 a.m. EDT. foxreno.com plans to carry the launch live.

Technicians still don't fully understand why one of the four hydrogen sensors in the external fuel tank gave a false reading July 13, forcing NASA to scrub that day's launch attempt.

Agency rules specify that all four sensors must work, although only two are needed. NASA has said that extra sensors are in place as backups.

NASA has re-wired some of the sensors and done extensive troubleshooting. A test director said he's confident the sensor will work properly Tuesday.

Discovery's flight will be the first for the shuttle program since the Columbia was destroyed on re-entry in 2003.

Mission Plan

The planned mission is to take a crew of seven to the international space station, where it will install a new gyroscope, among other tasks. They will also test methods for inspecting and repairing damage in flight.

There are three spacewalks planned during the mission.

Discovery is outfitted with a redesigned fuel tank and has dozens of motion and temperature sensors embedded in the wings to detect any blows from fuel-tank foam or other debris.