The installation of the $2bln Columbus segment, the first to be controlled by the European Space Agency, on the station's Harmony module was carried out by ISS Expedition 16 crew members Rex Walheim and Stanley Love.
Love replaced European Space Agency (ESA) astronaut Hans Schlegel, reported to be feeling ill, delaying Sunday's spacewalk until Monday. The German astronaut is expected to be fit to take part in a second spacewalk.
The astronauts also conducted some preparatory work to replace the Nitrogen Tank Assembly (NTA), a part of the space station's cooling system, scheduled for Wednesday and to be carried out by Walheim and Schlegel.
"As Columbus was moving into place, Walheim and Love began work to replace a large nitrogen tank used for pressurizing the station's ammonia cooling system," the official NASA website said.
Once activated the Columbus space laboratory, which has taken some 10 years to construct, will be the second ISS laboratory to go into operation since the Destiny module was delivered there in 2001.
The Columbus segment, which gives the ESA its first platform in space and the right to deploy a European astronaut for a six-month period every two years, will be controlled from a ground station in Germany.
The crew of the U.S. Atlantis shuttle, which docked with the ISS last Saturday, comprises seven astronauts - commander Stephen Frick, pilot Alan Poindexter, mission specialists Rex Walheim, Leland Melvin and Stanley Love plus ESA astronauts, Hans Schlegel from Germany and French national Leopold Eyharts.
In all, the crew of the U.S. shuttle is planned to carry out three spacewalks.
