Image: A closeup of the 7-inch quick disconnect that will be replaced on the hydrogen vent line to the Ground Umbilical Carrier Plate of space shuttle Discovery's external fuel tank. Photos courtesy of United Space Alliance

Repairs are under way on the Ground Umbilical Carrier Plate (GUCP) interface, where gaseous hydrogen leaked during Wednesday's launch attempt. The interface then will be retested and leak checked before Sunday's 7:43 p.m. launch attempt. The Mission Management Team will meet on Saturday at 1 p.m. to review the data and the progress of the teams, and make a final determination on the launch. A Prelaunch News Conference will be held no earlier than 3 p.m. following Saturday's MMT.

The weather forecast calls for an 80 percent chance of acceptable conditions at launch time. Meteorologists are watching for low cloud ceilings, Shuttle Weather Officer Kathy Winters said. The forecast deteriorates for potential Monday and Tuesday attempts.

The mission would last 13 days if Discovery launches Sunday. The astronauts would perform three spacewalks during the flight.

Discovery's astronauts awoke at 9 a.m. and underwent standard medical exams at 10 a.m. Commander Lee Archambault and Pilot Tony Antonelli will practice landings in the Shuttle Training Aircraft at 7 p.m.