( dpa ) - Astronauts on board the Atlantis space shuttle were preparing Sunday for a spacewalk on Monday to attach the Columbus space lab to the International Space Station (ISS) after a day's delay due to unspecified "health issues" with German astronaut Hans Schlegel.
Officials at the German Space Agency (DLR) mission control centre in Oberpfaffenhofen in southern Germany meanwhile said that Schlegel, 56, was now in "perfect" shape.
"Yesterday there were readings which called for caution," DLR official Andreas Schuetz said about Schlegel's problems on Saturday.
"Today it has turned out that he is in perfect form and there is nothing standing in the way of the second spacewalk (for Schlegel)," Schuetz said, referring to the follow-up outside work later in the mission.
However, Schlegel would not be taking part in the first space walk - which had originally been set for Sunday - to start the work to attach the European Space Agency's (ESA) Columbus module to the ISS.
He is to replaced by US astronaut Stan Love, who had already been scheduled for a spacewalk later in the mission.
With the one-day delay in the first spacewalk, NASA extended the Atlantis mission by a further day, with the shuttle now scheduled to return to earth on February 19.
NASA had declined to specify what Schlegel's "health issues" were, with a NASA official only commenting that they were not life- threatening.
But US media reports spoke of the well-known phenomenon of "space adapation sickness" in which astronauts suffer nausea and orientation problems. The TV network CNN, citing space experts, said 50 per cent of astronauts suffer from it and the problems usually go away after two to three days.
Schlegel himself sounded hearty in answering Sunday's morning's roll call and thanked the ground crew for the wake-up music, the song "Maenner" (Men) by German pop singer Herbert Groenemeyer.
The Atlantis, with its crew of seven, docked with the ISS at 17.17 GMT on Saturday after a two-day voyage on the mission in which the key task is attaching the Columbus space lab module to the orbiting station.
Besides Schlegel's health, NASA engineers were looking at two further problems. One involved a flight computer failure, whereby Shuttle flight director Mike Sarafin pointed out that there were two further such computers on board.
A second problem was a small tear in the thermal blanket on the right Orbital Maneuvering System pod. NASA said that "focused inspections" of the shuttle's thermal protection system were to take place later Sunday .
The arrival of the Columbus is a milestone for ESA programme engineers and officials at their headquarters. They have been waiting four years for their Columbus laboratory - Europe's largest contribution to the space station - to be installed to expand the scientific research capacity of the ISS.
The delay was triggered by the tragic 2003 loss of NASA's Columbia shuttle.