Could the new solar arrays be the source of the problems? In this image obtained from NASA video, U.S. astronaut Steve Swanson works at the base of a solar array on the International Space Station on 13 June.

Credit: NASA/AFP

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WASHINGTON: The International Space Station was rocked by hours of computer communications trouble Thursday, the latest problem the first space shuttle mission of the year has faced after a thermal blanket tear.

After hours of a glitch in Russian computers that control the International Space Station's (ISS) critical oxygen and water supplies, communications with the systems have resumed, U.S. space agency NASA spokesmen said.

"We are in a stable configuration," NASA associate administrator for space operations Bill Gerstenmaier told a news conference in Houston, Texas.

"We've got a challenge. We'll figure out a way to get this behind us. We've got time," he said, adding that there was "an extremely remote chance that this problem will lead to abandoning the space station."

Power outage

NASA spokesman Bill Jeffs said that the problem had arisen overnight with "computers going off-line," in the first such mishap of its kind, which raised concerns the mission might have to be cut short.

But now "they have re-established communications" with the module and Russian central computers, Jeffs said.

"The Russians report that they think it is a power problem and not a software problem" that triggered the potentially dangerous glitch, Jeffs said.

Indeed, the Russians believe the glitch with the Russian computers on board the ISS was probably caused by the solar panel installed by U.S. astronauts, a Russian space construction firm said Thursday.

"Russian specialists believe that the new solar panel installed by the Atlantis astronauts during their spacewalk could be the origin (of the breakdown)," said Irina Gomenyuk, a spokeswoman for Energia, which designed much of the station.

This "new powerful source of energy caused a malfunction of sensitive system elements" on the Russian and American segments of the station, in particular of the electrical supply system, Gomenyuk was quoted as saying by ITAR-TASS.

"Step in the right direction"

ISS flight director Holly Ridings added that the Russians "were able to re-establish communications with the central computer on board the Russian segment of the ISS.

"They have been able to send commands to the system in the service module ... It looks they made a lot of progress overnight (and) we'll talk to them as we have been doing all night through the next couple of days to understand what caused the issue," she said.

Another NASA spokesman, John Ira Petty, said the problem had not been entirely fixed by 12:55 GMT (21:55 Sydney time) Thursday, but that the communications reconnect was "certainly a step in that direction" after many hours of interruption.

"There is some cleaning up left to do after a situation like this as you can imagine. But we are optimistic," he added.

Two US astronauts spent more than seven hours outside the ISS on Wednesday working on its solar power panels as part of a huge expansion of the station's generation capacity.

Pat Forrester and Steve Swanson, who arrived at the ISS Sunday aboard the NASA space shuttle Atlantis, undertook the second of a total four spacewalks for construction and inspection purposes during the Atlantis's 13-day mission in space.

The two worked 90 minutes on a 73-metre older solar array on the starboard side of the ISS, "fluffing" it, NASA said, to ease full retraction on Thursday.

But they only succeeded in folding up 13 of the unit's 31.5 array bays before NASA took them off the job.

Insulation damage

The next space walk is scheduled for today, during which astronauts will try to repair a damaged insulation blanket on the Atlantis which peeled back after liftoff at the rear of the shuttle, exposing a small underlying area that theoretically could be hazardous to the graphite structures underneath as the craft returns to Earth.

NASA aims to have the astronauts pin the blanket back into place with surgical staples. It has played down concerns over the tear to the thermal blanket since it was noticed after last Friday's launch.

But such damage is a concern after the Columbia shuttle disintegrated as it returned to Earth in February 2003. This was due to breaks in its heat shield caused by foam insulation peeling off its fuel tank and striking a wing during the launch.

All seven astronauts aboard perished and the shuttle program was put on hold for nearly two and a half years while the space agency sought to overcome the problem, modifying the external fuel tank and setting procedures to check the heat shield while in orbit.