CAPE CANAVERAL, Fla. - German astronaut Hans Schlegel floated out of the international space station for his first spacewalk on Wednesday, two days after an illness forced the shuttle Atlantis crew member to skip an outing to install a new European lab.

Schlegel and American astronaut Rex Walheim ventured outside minutes before the space station passed over Cologne, Germany. They will spend the day replacing a nitrogen tank on the orbiting outpost.

"Hello to all the people of Germany," Walheim said. "What a pleasure it is to be up here spacewalking with one of your native sons, Hans Schlegel."

Schlegel said spacewalking is great.

"It's great to be a part of an international team ... doing research in space," he added.

In a series of broadcast interviews Tuesday, Schlegel said he was feeling great but was a little anxious about his first venture outside the safe confines of the cabin. He refused to say what had been ailing him, insisting "medical issues are private."

NASA and European Space Agency officials stressed there were no changes to Wednesday's 6 1/2-hour spacewalk on Schlegel's behalf, and that he would do everything just as he'd practiced before last week's launch. No one was opposed to his going outside to perform the strenuous spacewalking work, officials said.

Schlegel, 56, said Tuesday he backed NASA's decision to pull him off the first spacewalk because of his illness and delay Columbus' hookup by a day, even though it was a bitter pill.

"Nobody could have been happier than me when we finished (Monday's spacewalk) with the major objectives all done," he said.

Schlegel and the nine other space travelers spent Tuesday opening up the $2 billion Columbus lab and getting its equipment running. They were continuing that work Wednesday.

The astronauts -- wearing goggles to guard against floating dust, metal chips or other debris -- opened up floor panels to get to the equipment underneath, and turned on computers, heaters and fans. A few of the systems had startup trouble, but that's normal for a brand new piece of hardware, NASA managers said.

The European space station program manager, Alan Thirkettle, said it was thrilling to see astronauts inside Columbus, which was immaculate and brilliantly white.

"They're doing the first thing that the crew does, which is to make a complete mess of what was a beautiful piece of clean hardware inside," Thirkettle joked.

Atlantis will remain at the space station until at least Sunday. NASA is considering keeping the shuttle there an extra day.