Astronauts focused on inspecting a damaged thermal blanket on the shuttle Atlantis after the main job task of installing the Columbus lab had to be scrapped.
German astronaut Hans Schlegel developed a medical problem described as not life-threatening shortly after arriving at the International Space Station on Saturday.
As a result, he was pulled off the first spacewalk, although he sounded okay on Sunday morning.
"Greetings to everybody in America, in Europe and in Germany, and especially of course to my close family and my lovely wife, Heike," he said.
It isn't known yet if Schlegel, who has been to space twice before, will take part in the spacewalk scheduled for Wednesday.
Sunday's task of unloading the US$2 billion module Columbus will take place on Monday. The space station crew and shuttle astronauts did some preparatory work for that.
However, they will spend a substantial part of their day taking a closer look at a protruding part of the shuttle's thermal blanket.
There is an approximately four-centimetre by four-centimetre portion sticking up back near Atlantis's tail cover the right orbital manoeuvring system pod.
The damage occurred during Thursday's launch and was discovered Friday.
Space station flight director Ron Spencer said early Sunday that NASA wants to determine if the blanket is torn or just sticking up a bit.
The section is smaller than one that required repairs to Atlantis in June.
Thermal shielding problems led to the destruction of the Columbia shuttle in February 2003.
With files from The Associated Press
