The Endeavour astronauts were cleared today to unfurl a second solar array on the international space station, using a stop-and-start approach to avoid stressing tension cables designed to keep the array blankets taut.

The starboard wing of the station's new P6 solar array was deployed Sunday during a seven-hour 33-minute spacewalk by astronauts Joseph Tanner and Carlos Noriega.

But release of the array's 115-foot port-side wing was held up because of concern about how the starboard wing extended.

One of the two flexible solar cells blankets making up the starboard wing appeared to unfurl normally. But the other blanket is not as taut as engineers would like, apparently because a system of cables used to apply tension to the base of the blanket did not work properly.

During extension of the wing's central mast, the blankets rippled back and forth, oscillating dynamically as blanket panels bunched up and then pulled free. The astronauts said today the behavior of the blankets was alarming enough for them to consider halting the deployment.

"We were thinking about, talking on the flight deck about whether we should stop or not," Tanner told a reporter today. "We can't go any slower, there's only one rate those will deploy unless you do it manually.

"We were watching it closely and the panels were sticking together and as it continued to deploy, the panels would unstick and it was pretty dynamic there for a while. ... It was like you were loading up a spring and then it would release.

"The tension mechanism is a spring, basically, and as it stretched out it put enough tension on the stuck panels to cause them to break loose," Tanner said. "Then the spring would retract again and the process would keep occurring as the panels broke loose."

Commander Brent Jett said the crew was "a little bit surprised by where the arrays were sticking and how much the tension bar was being pulled out."

After studying closeup video views of the blankets, NASA managers decided today to press ahead with deployment of the port-side wing.

But instead of letting the deployment proceed unchecked at one constant speed from start to finish, they told the crew to turn the wing's mast extension motor off and on to minimize stress on the tension cables and to let any oscillations damp out.

As for the slack panel on the starboard array, Jett told flight controllers early today that Tanner and Noriega would be willing to attempt repairs during a spacewalk Tuesday.

"The more we look at that left blanket box on the starboard array, the tensioning cables, they don't really appear to be broken, it looks like they might be off track or have jumped off the mechanism," he said.

"We were thinking about maybe another way to tension the arrays using PRDs (payload retention devices) to tension it and a long tether to secure it.

Tanner said the main problem with attempting any repairs is that the wings are so high above the shuttle's cargo bay - 90 feet or more - making them difficult to reach.

"There are not too many options because the worksite is very high," he said. "One thought we've had here is Carlos gets in an APFR (articulating portable foot restraint) and then holds my feet and we essentially become a stack of two people to get me up high enough to get a tether around the tension bar to pull it down. It should be exciting if we try it."

But the spacewalkers never practiced such a procedure during training.

"Unfortunately, this is not one case we simmed or even dreamed about," Noriega said. "This tension bar one is unfortunately one of those we didn't anticipate. And those are the ones that usually catch you."