HOUSTON — With two of their three spacewalks completed, the astronauts aboard the linked shuttle-station complex focused Thursday on getting the new Columbus lab up and running.

NASA extended Atlantis' mission by a day on Wednesday to give the crew more time to work on the lab, Europe's main contribution to the international space station.

Computer problems that had hindered the activation process were fixed by Thursday, and the space station crew hoped to be able to begin science operations as soon as Atlantis departs next week.

"For me, it's still hard to believe that it's real," French astronaut Leopold Eyharts told German Chancellor Angela Merkel and European Space Agency chief Jean-Jacques Dordain in a Thursday broadcast from inside Columbus.

Speaking in German, Merkel said she is very happy that Europe has increased its participation in space station research.

"We are now acquiring more knowledge, and this also brings more respect for what we're doing," she said.

Merkel had several questions for German astronaut Hans Schlegel, including one about how he is feeling, an apparent reference to the illness that forced NASA to pull him from Monday's spacewalk to install Columbus.

Schlegel, 56, has declined to discuss his condition and did not mention it in his answer, instead talking about how perfectly the Columbus module is working.

"We feel excellent, and it couldn't be any better," he said.

Schlegel looked and sounded fit on Wednesday as he participated in a nearly seven-hour spacewalk to replace a depleted nitrogen tank from the space station. The high-pressure nitrogen gas is needed to flush ammonia through the station's cooling lines.

Dordain said Europe was proud to watch his spacewalk.

"After a while of getting used to it, I think I felt like I had been there already several times," Schlegel said, praising the ground teams that trained him for the spacewalk. "It went from my point of view very well."

The crew also spent much of Thursday preparing for the next day's spacewalk to attach a pair of science experiments to the outside of Columbus.

Spacewalkers Rex Walheim and Stanley Love also plan to inspect a damaged handrail that may have caused glove problems for spacewalkers in past missions. Spacewalking astronauts have ripped their gloves three times over the past year.

If they have time, Walheim and Love will also perform another inspection of a jammed joint that is needed to turn one of the space station's two sets of huge solar wings. NASA has been studying the problem for months and wants a few more pictures.

The same joint on the other side of the station unexpectedly shut down due to a computer glitch early Thursday, but NASA quickly got it working again.

Atlantis will remain at the space station until Monday. That makes for a 13-day flight, with touchdown now set for Feb. 20. The shuttle's thermal shielding has been completely cleared for re-entry.