Seven astronauts boarded the space shuttle Discovery, hoping for a break in gusty Florida winds and the start of a complicated mission to rewire the International Space Station.
Updated at 7.40 am:
Irene Klotz
CAPE CANAVERAL (Florida): The United States space shuttle Discovery's two rocket boosters separated from the orbiter Saturday, two minutes into its night launch toward the International Space Station.
The shuttle later rocketed into orbit.
Earlier, seven astronauts boarded the space shuttle, hoping for a break in gusty Florida winds and the start of a complicated mission to rewire the ISS.
Discovery blasted off from the Kennedy Space Center in NASA's first launch after sunset since before the 2003 Columbia disaster.
Managers recently lifted the ban on night launches, imposed to ensure cameras had good lighting to spot debris falling off the shuttle's fuel tank.
Debris hit Columbia during launch and caused damage that led to the shuttle's breakup as it returned through the atmosphere for landing, killing all seven crew aboard.
As the Discovery astronauts made their way into the shuttle, forecasters upgraded the weather outlook a bit, but still predicted a 60 percent chance that high winds or clouds would keep the shuttle grounded until at least Sunday.
Poor weather forced NASA to cancel the shuttle's first launch attempt on Thursday.
''Here we go again,'' launch commentator Bruce Buckingham said as the crew headed toward a van for the ride to the seaside launch pad.
Earlier on Saturday, the astronauts enjoyed a pre-launch meal of lobster, steak and salmon. The two Europeans aboard -- Sweden's Christer Fuglesang and London-born Nicholas Patrick -- opted for hamburgers and fries.
Sunita Williams, who will stay behind on the space station after the shuttle departs, made do with lighter fare: a grilled cheese sandwich and tomato soup.
NASA hopes to get its third and final shuttle mission of the year airborne before December 17 and avoid a potentially troublesome and time-consuming effort to update Discovery's computers during flight to accommodate the transition to the new year.
The shuttle's computers, not designed to fly through a year-end rollover, would fall out of sync with ground-based systems.
The goal of Discovery's 12-day flight, which would be the 117th in shuttle program history, is to rewire the International Space Station so partner laboratories built by Europe and Japan can be installed next year.
The crew was strapped in and ready for an initial launch attempt on Thursday night but a thick ceiling of clouds failed to part before the Earth rotated out of position for Discovery to reach the space station.
Friday's weather was too poor to even attempt a launch. NASA needs good visibility to track the shuttle at liftoff, and the winds have to be calm enough to permit a landing in case of an emergency.
The crew includes five first-time fliers: Fuglesang, Patrick, Williams, Joan Higginbotham and pilot William Oefelein. In command is Mark Polansky, who is making his second flight. Robert Curbeam, the flight engineer and lead spacewalker, is flying for the third time.
Landing will be targeted for December 21 at the Kennedy Space Center.