CAPE CANAVERAL, Fla. (AP) – After a handful of unsuccessful attempts Friday to coax a solar array to fold properly, NASA officials now plan to send two spacewalkers to examine it close up and may add a fourth spacewalk if needed.

Astronauts Robert Curbeam and Sunita Williams, scheduled on Saturday to perform the last of three planned spacewalks of the space shuttle Discovery mission, will also examine the solar wing if their main rewiring task is successful and completed with time to spare.

“We’re currently envisioning this as an inspection task. How much and what you could touch and what kind of good it could do is still very much under discussion,” Mission Control astronaut Steve Robinson radioed up to the crew on the international space station.

“So right now, think of it as going up and taking a good close look and telling us what’s really going on,” Robinson said.

NASA suspects the problem is with “recalcitrant grommets” in the solar wing, where a guidewire is thought to be stuck.

Robinson also told the crew that back-to-back spacewalks are not an option, so if NASA decides to send astronauts out on a fourth foray to manually help the wing fold, it would be Monday at the earliest.

The announcement came shortly after the crew pulled and pushed on the solar wing – ending pretty much where they started. As on Wednesday, the wing stalled in a particular section where NASA believes a wire is caught in some eyelets.

Earlier Friday, flight controllers jiggled the solar array by remote control to try to relieve tension in a wire system that is preventing it from folding up like an accordion, as designed – but to no avail.

German astronaut Thomas Reiter of the European Space Agency, a space station resident, was told to do 30 seconds of robust exercise on a bungee-bar machine in an attempt to vibrate wires on the 115-foot solar array.

Reiter’s exercise did not appear to change the solar array.

Flight controllers thought the workout might fix the solar array problem because of a previous incident in which the space agency saw an array shaking and found it was caused by an astronaut working the exercise device hard.

The solar wing is part of an interim power system. A primary goal of Discovery’s seven-day visit to the space station was to rewire the lab and hook a new set of solar wings onto the permanent electricity grid.

The new panels rotate with the movement of the sun to maximize the amount of solar energy produced, but in order for the new panels to spin, the old panel had to be retracted.

“You’ve probably heard us use the analogy of trying to fold a map,” U.S. astronaut Michael Lopez-Alegria, a space station crew member, said during a news conference from space. “At times, when you’re folding a map, it’s helpful to poke it here and there. … It won’t be very different from that, although we’ll be poking very gently.”

The old solar array could be jettisoned in a worst-case scenario.

During two previous spacewalks, the Discovery crew installed a 2-ton, $11-million addition to the space station and rewired half of the orbiting space lab. The third spacewalk is scheduled to rewire the other half.

Curbeam, a U.S. astronaut, and Swedish astronaut Christer Fuglesang – who have performed both of the spacewalks – would likely conduct the fourth spacewalk, if needed. It could also be performed later by one of the space station crew members.

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