Astronauts prepare for extra spacewalk

Astronauts spent yesterday preparing for an extra spacewalk to free a stuck solar array on the International Space Station and unloading supplies brought up by the shuttle Discovery.

"It may be a quiet day in terms of conversation... but it's a busy day for transfer and preparation for (today's) spacewalk," Nasa spokesman Kyle Herring said as crews in space worked with minimal air-to-ground chatter.

The mission to supply and continue building the station, due for completion in 2010, has been extended a day to accommodate the additional spacewalk. It will be the fourth outing of the flight.

Mission managers said they were "very confident" crews, with the help of spacewalkers, would complete folding the 33-metre-long array into a 50-cm-high box so it can be relocated in future space station construction. Discovery is now scheduled to land Friday after 13 days in space instead of Thursday after 12 days as originally planned.

The jammed array, one of eight that will convert the sun's rays into electric power for the space station, has been a blot on a mission to rewire the station to get ready to add laboratories built by Europe and Japan.

Snags reeling in the panel are not a complete surprise. It is wafer-thin and folds like a set of window blinds, though much more carefully. It had sat unfurled in space for six years, enduring alternating blistering heat and frigid cold.

Astronauts Robert Curbeam, who will set a record with his fourth outing this mission, and Christer Fuglesang spent yesterday readying spacesuits and other equipment for their spacewalk. They were to sleep in an airlock overnight to get ready.

The working excursion is set to start about 12:30 p.m. central time (1830 GMT) today and last as long as six-and-a-half hours. "The length of the spacewalk is contingent on retraction of the array," Nasa spokesman Kyle Herring said.

It will be the second use of spacewalkers to try to complete pulling in the panel after it failed to fold up by remote control as planned on Wednesday.

The panel retracted far enough by electronic command to allow another set of panels installed in September to rotate and track the sun, but full retraction is needed to smooth the way for future construction missions.

Mr Curbeam and first-time spacewalker Sunita Williams worked on the stubborn panel on Saturday after they finished rewiring the station. They shook it by hand, and ground controllers got it two-thirds retracted before time ran out on the spacewalk.

Officials said Nasa will use lessons learned wrestling with the panel on the next shuttle mission, which is scheduled to retract the other half of the troublesome panel.

In other work yesterday, astronauts were expected to finish 95 per cent of the task of transferring supplies to the space station and loading discarded material onto Discovery for the trip back to Earth.