NASA engineers worked Friday to fix a fuel leak in time for this weekend's launch of the space shuttle.
Discovery is set to launch from the Kennedy Space Center in Florida at 7:43 p.m. Sunday. Discovery's liftoff was postponed because of a hydrogen gas leak during Wednesday's launch attempt.
The seven shuttle astronauts are scheduled to install the last set of solar electricity panels on the International Space Station, but they'll be pressed for time because a Russian Soyuz capsule is expected at the space station later this month.
If Discovery launches Sunday, the mission will last for 13 days. NASA officials have shortened the mission and decreased the number of spacewalks scheduled to three, so Discovery will be undocked and out of the way by the time Soyuz arrives.
At a news conference Friday morning, NASA weather officer Kathy Winters said there's an 80 percent chance that weather conditions at the launch site will be acceptable Sunday. The weather is expected to worsen on Monday and Tuesday.
If Discovery doesn't launch by Tuesday, NASA officials may be forced to move the shuttle mission to early April to accommodate the Soyuz visit to the space station.
The crew had a close call on Thursday when a piece of space junk hurled past the space station. The crew took refuge for 10 minutes inside a Russian capsule docked at the space station. NASA officials feared the crew might have to make a quick getaway if the debris struck and damaged the station.