NASA tackles station's jammed solar array

Houston, Dec 16: NASA ground controllers tried to free a jammed solar panel on the International Space Station while astronauts prepared for a final spacewalk to rewire the outpost's power grid.

The 33-metre panel was retracted enough to allow new solar arrays to rotate and track the sun for power. But NASA needs the whole span folded up into a storage box so the array can be moved to a new position next year and returned to service.

Flight controllers tried to shake the balky wing and free a tension wire that was either blocked or rubbing against a protective eyelet at the base of the array.

''I didn't see any change,'' shuttle commander Mark Polansky told Mission Control yesterday. ''It looks like the guide wire has the same amount of tension, or lack thereof, as when we started.'' Space station crew member Thomas Reiter did his bid to free the array, vigorously exercising on a resistance machine that in the past had been shown to vibrate the panels.

''I was training for that for half a year,'' Reiter joked.

The array, however, remained jammed.

If the wing panel cannot be fixed by remote control, NASA is considering adding a fourth spacewalk to the shuttle Discovery crew's job list to fix the array before the shuttle leaves the outpost.

''It doesn't need much coaxing,'' station commander Michael Lopez-Alegria said during an in-flight news conference.

Retracting the array is like folding a map, he added.

''It's helpful to poke it here and there. I think this will not be very different than that, although we'll be poking gently,'' Lopez-Alegria said.

POWER UPGRADE

The panel is studded with delicate solar cells. The array is one of two that provided power to the US sections of the station until astronauts rewired the station to draw power from a new set of arrays installed during the last shuttle flight in September. The rest of the rewiring is scheduled to be finished during another spacewalk today.

The station needs the power upgrade to support additional laboratories due to arrive next year.

The first attempt to fold the panel on Wednesday was called off after more than six hours of work. NASA is expected to decide by this morning whether to dispatch Discovery's spacewalkers to fix the array, or leave it for the station crew or the next shuttle crew to handle.

While engineers considered what to do with the array, the shuttle crew took a few hours' break as they passed the halfway point of their planned 12-day mission.

Astronaut Christer Fuglesang, the first from his native Sweden to fly in space, took advantage of the zero-gravity to attempt a world record for the longest Frisbee toss.

''I might need a few trials, because sometimes it's hard to get it to stay,'' said Fuglesang, gently blowing on the disc to keep it spinning.

Discovery's homecoming is scheduled for Thursday at the Kennedy Space Center in Florida.

It is the fourth shuttle mission since Columbia broke apart over Texas in 2003, killing the seven astronauts aboard and grounding the shuttle fleet for more than two years. Two shuttle flights in 2005 and earlier this year tested safety upgrades and a third, in September, restarted construction of the 0 billion space station.

REUTERS