The shuttle's fiery ascent Saturday turned night into day for spectators at the Kennedy Space Center. A cloudy sky with blustery winds earlier in the day gave way to clear skies and a gentle breeze at launch time.

Space Shuttle Discovery lifts off from launch pad 39B with a crew of seven at the Kennedy Space Center, Fla. Saturday Dec. 9, 2006. STS-116 twelve day mission will service the International Space Station. [AP] More photos: Space shuttle Discovery lists off at night

"I think we have five people who just haven't stopped smiling yet," commander Mark Polansky said after Discovery reached space.

The mission is one leg of a three-year race to finish construction on the orbiting outpost before shuttles are retired in 2010.

Low clouds forced the space agency to scrub a launch attempt Thursday night during a countdown that ran down to the wire. Managers decided not to try again Friday because the forecast looked even worse.

"Forty-eight hours makes a tremendous difference," launch director Mike Leinbach told the crew.

During their 12-day mission, Discovery's crew will rewire the space station, deliver an $11 million (euro8.3 million) addition to the space lab and bring home one of the space station's three crew members, German astronaut Thomas Reiter of the European Space Agency. American astronaut Sunita "Suni" Williams will replace him, staying for six months.

The launch was the first at night since Endeavour's flight in November 2002 and only the 29th in darkness of NASA's 117 total shuttle launches.

NASA had required daylight launches for three flights after the Columbia accident in 2003 so that clear images could be taken of the external fuel tank. Foam breaking off the tank and striking Columbia's wing at liftoff led to the disaster that killed seven astronauts.

Waiting at the space station for his visitors to arrive on Monday, U.S. astronaut Michael Lopez-Alegria told Mission Control: "We're going to head out and turn our porch light on so they can find us."

Referring to Williams's first flight, Lopez-Alegria told the shuttle crew: "I hope Suni likes it. She's going to be there for a while."

Discovery's crew is the greenest in eight years when it comes to spaceflight experience. Five astronauts have never flown in a shuttle before. The last time a shuttle mission had five rookies was a Columbia crew that flew in April 1998.

The two veterans are commander Polansky and Robert Curbeam, who will spacewalk three times. The others are pilot William Oefelein, and mission specialists Joan Higginbotham, Nicholas Patrick, Williams and the European Space Agency's Christer Fuglesang, who was the first Swede in space.

It also is among the most culturally diverse of any shuttle crew.

Besides the Swede, there are also two black astronauts, an astronaut of Indian descent and a British-born mission specialist.

Three of Discovery's astronauts will take three complicated spacewalks and play the role of electricians by rewiring the space station from a temporary to a permanent power source.

NASA officials were glad to get the shuttle off their ground since they wanted it back on Earth by the new year.

Shuttle computers are not designed to make the change from the 365th day of the old year to the first day of the new year while in flight. The space agency has figured out a solution for the New Year's Day problem, but managers are reluctant to try it.

It was the third shuttle launch of the year, and only the fourth since the Columbia disaster in 2003.