(Agencies)
Updated: 2008-02-05 06:30

CAPE CANAVERAL, Florida - Seven astronauts returned to NASA's launch site Monday to take a new shot at flying space shuttle Atlantis to the international space station.

Liftoff is set for Thursday afternoon, with NASA wrapping up a last repair Sunday night involving a radiator hose. The mission was waylaid in December by a different problem, erratic fuel gauges.

Atlantis will carry the European Space Agency's science lab, Columbus, to the orbiting outpost. That will be the second science lab - the United States operates one there already. The largest lab of all, Japan's Kibo, or Hope, will be carried up in sections beginning next month.

Atlantis' mission, fraught for weeks with mechanical problems, now faces only weather concerns, NASA officials said.

As the countdown clocks began ticking late Monday afternoon, forecasters put the odds of acceptable conditions at just 40 percent because of a cold front and rain expected on launch day. Friday's outlook was much better: 80 percent.

Shuttle commander Stephen Frick said he was satisfied with the repairs to the fuel gauge system, which has troubled NASA for the past few years, and was happy the shuttle team finally succeeded in "nailing this thing down and fixing it."

"We're feeling very good about this opportunity. We'll keep looking at the weather, but we're very happy about the condition of Atlantis," Frick said.

The fuel gauge problem was traced to a bad connector at the bottom of the shuttle's huge external fuel tank. The external portion of the connector was replaced with a newly soldered unit.

On Sunday night, a NASA technician was able to tuck a bent radiator hose into its payload bay retraction box.

NASA still hopes to get six shuttle launches off this year, even with Atlantis' two-month delay. The space station faces a 2010 completion date. Then, the three remaining shuttles will be retired so the space agency can focus on returning astronauts to the moon, with eventual plans to fly to Mars.

In a video hookup with family members and friends in Ireland on Monday, space station astronaut Daniel Tani was asked by a young boy if he'd ever been to Mars.

"No, unfortunately, I have not been on Mars. In fact, no people have been on Mars yet. Mars is a long way away. It's going to take a long time to get there, but we're working toward it," said Tani, whose wife, Jane, is from Cork.

Tani, in orbit since October, will return to Earth aboard Atlantis. A French Air Force general will fly up on Atlantis and take his place.

"Hopefully, they'll launch this Thursday and I'll be home in a couple weeks," Tani said.