The solar arrays were successfully unfurled, but flight controllers couldn't use stabilizing gyroscopes, they used shuttle rocket thrusters instead. That resulted in solar power loss from the left array, which couldn't properly track the sun. Computer hang up also turned fire alarm on without any reason.

Later Johnson Space Center in Houston used a new, yet untied technique to switch the flight controllers to the stabilizing gyroscopes without using the Russian computer's system. But after this technique got used, an alarm was turned off forcing to switch to digital autopilot.

Computer hang up caused troubles, of course, but Atlantis crew had lucky moments as well. New S3/S4 solar arrays were successfully unfurled at the right side of the power truss.

"As a program guy, I'd be remiss if I didn't tell you what these solar arrays mean to us," said Mike Suffredini, NASA's space station program manager at the Johnson Space Center in Houston. "This set of solar arrays will provide about 20 kilowatts of power to the international space station. That's useable power. It provides quite a bit more than that, but some of it is siphoned off to take care of its own systems."

"That equates to something like eight to 10 households," he said. "So it's a significant amount of power we bring to the space station now. In addition to that, it's going to allow us to take our next steps, which begin early tomorrow morning and that'll be the retraction of the 2B array."

The power truss has four solar arrays. The left side is equipped with P4, set up last September, and newly set up S3. The right side of the truss has P6-4B and P6-2B solar arrays. P6-4B was planned to be replaced last December engineers had problems with setting it up, so it still needs to be replaced. And P6-2B is planned to be replaced by Atlantis crew later this week.

Now astronauts are watching how S4 tracks the sun. If it doesn't do it smoothly the astronauts will fix the array manually during a 6.5 hour spacewalk. By Ruzan Harutyunyan For HULIQ