Astronauts from the space shuttle Discovery have struggled through a difficult day thanks to a mysterious pressure leak and worries about some critical flight software.
The major morning job for the Discovery crew, which has been working on the International Space Station for more than a week, was to remove the Italian-made Leonardo cargo module from the station and return it to the shuttle for the return flight to Earth.
But a small vestibule compartment between the space-station and the 21-foot cylindrical module twice began to refill with air after the crew tried to depressurise it.
NASA was about to send an astronaut into the compartment to investigate when one of the space-station crew, James Voss, discovered the problem - a leaky connection on an air hose that could be safely ignored.
Earlier, the Discovery crew spent hours testing the software on two shuttle computers that had been turned on too quickly.
Despite a series of delays, the shuttle crew has met all their mission objectives. They delivered about five tons of supplies and hardware to the station along with the second crew to take up residence.
They also installed the first early components of a Canadian-built robot arm that will arrive at the station next month. The arm is a bigger, smarter and more dexterous version of the one that Australian astronaut Andy Thomas used to pluck Leonardo from the space station's walls and nestle it in the shuttle's payload bay.
The computer software problem could have delayed the shuttle's return to Earth by yet another day if the software had been corrupted and had to be reloaded.
Two of the shuttle's General Purpose Computers were turned on too quickly Saturday. Guidelines call for them to be activated 10 seconds apart, but the astronauts, who were not working from a set procedure, took only six seconds, NASA said. Four computers in all might have been effected by corrupted software.
NASA had Wetherbee and pilot James Kelly run the lengthy diagnostic test to reassure ground teams that the computers were operating normally.
"We have full confidence that things will work from now on," Mission Control told the astronauts.
The US$150 million Leonardo module is making its maiden flight. The space station, still under construction, is a joint project of space agencies in the United States, Russia, Europe, Japan and Canada. NASA expects to spend US$95 billion to build and then operate the facility for a decade or more.
