Astronauts try to fold space station's solar wing

HOUSTON, Dec 13 (Reuters) Astronauts aboard the International Space Station began the delicate task of folding up one of the station's solar power wing panels today to make way for a new set to track the sun for power.

If the 120-foot-ong panel does not retract as planned after six years in space, NASA could decide to send out the space shuttle Discovery's spacewalkers to manually crank in the panel.

The panel needs to be folded up by at least 40 percent to provide clearance so a set of solar arrays installed during the last shuttle mission in September can pivot.

''This is a major milestone for the program,'' station flight director John Curry said at a briefing late yesterday.

The crew of the space shuttle Discovery, which arrived at the station on Monday for a weeklong stay, needs to rewire the station's electrical system to tap power produced by the new solar panels.

The rewiring will pave the way for laboratories built by Europe and Japan to be attached to the space station beginning next year.

The work had initially been planned for 2003 but NASA halted space station construction after the destruction of the shuttle Columbia.

Assembly resumed in September, with a new deadline to complete the outpost before the shuttle fleet is retired in 2010. NASA needs at least another 13 missions to finish the complex.

The old array is one of two that have been operating since 2000 from a temporary location on top of the station. The second array is scheduled to be folded up next year.

Engineers are concerned the panel may not fold as planned, having been subjected to the extreme heat and cold of space for years.

''That's a big deal because this thing wasn't supposed to stay extended so long. We're going to be watching like a hawk to make sure it happens just right,'' Discovery astronaut Bill Oefelein said in a preflight interview.

Added Curry, ''I will be pleasantly surprised if everything works there without a hitch.'' The shuttle crew positioned their ship's robot arm so cameras mounted on the boom would have a good view of the panels as they folded, accordion-style, into a flat box.

If the array should fail to retract as planned, NASA could decide to send out Discovery's spacewalkers to manually crank in the panel.

Astronauts Robert Curbeam and Christer Fuglesang completed the first of three planned spacewalks yesterday, successfully installing a new metal piece to the station's backbone.

As the spacewalk was wrapping up, NASA got word of a powerful solar flare that discharged higher levels of x-ray radiation and charged particles toward Earth. Flight controllers told the commanders of the shuttle and the station to have their crews sleep in protected parts of their ships.

The radioactive environment is not expected to impact plans for spacewalks tomorrow and Saturday, though NASA will continue to monitor the space weather, Johnson Space Center spokesman Bill Jeffs said.

REUTERS DKS PM0146