( dpa ) - Europe's newest and most important addition to the space station, the Columbus laboratory, was being dressed up Friday with added experiments and observatories during a spacewalk.
US astronauts Rex Walheim and Stanley Love got an early start at 1307 GMT - more than half an hour ahead of schedule - to tackle the day's tasks, NASA officials said.
At the top of the agenda was installing two European science projects - an observatory to monitor the sun for two years, called appropriately SOLAR, and the European Technology Exposure Facility (EuTEF), which carries nine experiments requiring exposure to the space environment.
In a moment of high space drama Monday, the International Space Station team, including Love and Walheim on the outside and a robotic arm operated from inside, removed the 4.5-metre-diameter cylindrical Columbus from the Atlantis shuttle cargo bay and installed it permanently on the station.
The European Space Agency had to wait four years for the moment as the NASA shuttle programme recovered from the 2003 Columbia shuttle disaster and tested new safety programmes.
During its 10-year life span, Columbus is to host thousands of experiments in life and materials science, fluid physics and other disciplines.
Atlantis and its seven astronauts are to undock at 0926 GMT Monday from the space station and land back on Earth on Wednesday.