HOUSTON — The crew of the space shuttle Atlantis replaced a nitrogen tank outside the International Space Station on Wednesday with the help of German astronaut Hans Schlegel, who missed an earlier spacewalk to install the European science lab because of illness.

Schlegel got a chance Wednesday to climb across the laboratory module dubbed "Columbus" built by the European Space Agency.

"I'm holding on to Columbus," Schlegel said. "It's a good feeling."

The Columbus module added 500 cubic meters to the space station when it was installed Monday and opened Tuesday.

"Welcome to spacewalking, Hans," said veteran spacewalker Rex Walheim. Schlegel and Walheim replaced a refrigerator-size nitrogen tank. Nitrogen in the tank pressurizes the space station's cooling system. Walheim held each tank as the space station robot arm swung him from the payload bay to the space station and back.

"This is a great ride!" Walheim said.

The spacewalkers also examined a ding in a space station handle that spacewalker Stanley Love spotted Monday. Several astronauts have damaged their gloves, and this rough spot, possible caused by a micrometeoroid, could be a reason.

As the six-and-a-half-hour spacewalk came to a close, Schlegel said, "It's an incredible view."

He missed his first spacewalk Monday because of a medical condition that neither NASA nor he would disclose. Love replaced him, and Schlegel apparently recovered.