Endeavour and six astronauts rocketed into orbit Monday on what's expected to be the last nighttime launch for the shuttle program, hauling up a new room and observation deck for the International Space Station.

The space shuttle took flight before dawn, igniting the sky with a brilliant flash seen for miles around. The weather cooperated at the last minute: Sunday morning's try was thwarted by thick, low clouds that returned and almost caused another delay.

"Looks like the weather came together tonight," launch director Mike Leinbach told the astronauts right before liftoff. "It's time to go fly."

"We'll see you in a couple weeks," replied commander George Zamka. He repeated: "It's time to go fly."

Endeavour's destination _ the space station, home to five men _ was soaring over Romania at the time of liftoff. The shuttle is set to arrive at the station early Wednesday.

Commander George Zamka and his crew will deliver and install Tranquility, a new room that will eventually house life-support equipment, exercise machines and a toilet, as well as a seven-windowed dome. The lookout has the biggest window ever sent into space: a circle 31 inches across.

It will be the last major construction job at the space station. No more big pieces like that are left to fly.

Both the new room and dome _ together exceeding $400 million _ were supplied by the European Space Agency.

Monday morning's countdown ended up being uneventful, except for a last-minute run to the launch pad. Astronaut Stephen Robinson forgot the binder holding all his flight data files, and the emergency red team had to rush it out to him, just before he climbed aboard. The launch team couldn't resist some gentle teasing.

The 13-day shuttle mission comes at one of the most agonizing times for NASA. Exactly one week ago, the space agency finally got its marching orders from President Barack Obama: Ditch the back-to-the-moon Constellation program and its Ares rockets, and pack on the research for an as-yet-unspecified rocket and destination.

NASA's boss, ex-astronaut Charles Bolden, favors Mars. But he, too, is waiting to hear how everything will play out.

The space station came out a winner in the Obama plan. The president's budget would keep the outpost flying until at least 2020, a major extension.

NASA's spectacular night-into-day finale attracted a crowd, including some members of Congress and federal bigshots. Endeavour shot through some thin clouds on its way into orbit. The shuttle's bright flame was visible for more than four minutes from the launch site.

More than 100 Europeans also were on hand because of the Italian-built Tranquility and domed cupola.

The four remaining shuttle flights to the station _ in March, May, July and September _ have daytime departures, at least for now. A significant delay could bump any of the launches into darkness. NASA has Obama's permission to bump a mission or two into 2011 if safety needs arise.

Given all the changes coming, the mood around the launching site was bittersweet.

The manager in charge of preparing Endeavour for launch, Dana Hutcherson, said everyone was excited to be part of the first launch of the new year.

"But let's face it, our KSC (Kennedy) team is going to have a challenging year ahead of us as the space shuttle is ending," she said. "It's not going to be easy for us."

Three spacewalks are planned during Endeavour's flight to hook up the new station compartments, beginning Thursday. The shuttle crew _ five men and one woman, all Americans _ will team up with the station residents to get the job done. Aboard the station are two Americans, two Russians and one Japanese.

Bolden sees that same blend of nations in NASA's future exploration efforts, whatever they are.

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On the Net:

NASA: http://www.nasa.gov/mission_pages/shuttle/main/index.html