Workers look over the replacement liquid hydrogen recirculation line (left) and the just-removed damaged one (right). Photo NASA/KSC

NASA today cleared shuttle Discovery for launch Thursday on the long-awaited mission to restore the Hubble Space Telescope to working order.

Workers successfully replaced a damaged liquid hydrogen recirculation fuel line aboard the shuttle on Friday and Saturday, and later testing found no problems, officials said Monday.

The 10-day Hubble repair mission is running two months late because of an assortment of wiring and other problems. But with this latest glitch resolved, Discovery is poised to lift off from Kennedy Space Center at 9:18 p.m. EST Thursday (0218 GMT Friday).

U.S. Air Force weather forecasters say there is an 80 percent chance of acceptable conditions on Thursday night.

"We are pushing for the 16th," NASA spokesman Joel Wells said. "We are 12 hours ahead of schedule."

Workers expect to have the aft engine compartment of Discovery closed for flight this afternoon. The three-day launch countdown would then start at 1:30 a.m. EST (0630 GMT) on Tuesday.

If Discovery doesn't make it off the ground on Thursday, NASA will have opportunities on Friday and Saturday nights to launch the shuttle, or else wait until January.

Discovery's seven astronauts plan to conduct four spacewalks to fix Hubble's broken pointing system and install other electronics.