Atlantis casts off, prepares for reentry

Space shuttle Atlantis undocked from the International Space Station on Tuesday morning, concluding a 10-day visit that featured the installation of a new set of solar power panels and an unexpected shutdown of Russian computers controlling the station’s oxygen supply.

After casting off at 7:42 a.m. Pacific time, the shuttle flew once around the station to allow the shuttle crew to take pictures of the new construction.

Later in the day, the shuttle crew used Atlantis’ robotic arm to scan the craft’s heat protection system. The crew was searching for any damage caused by space junk or small meteorites striking the shuttle while it was docked at the space station. Ground analysts were scrutinizing one object seen floating between the shuttle and the station. They are still unsure of its size or origin.

If the images come up clean, ground controllers will authorize Atlantis to enter the Earth’s atmosphere for a landing Thursday morning at Kennedy Space Center.

NASA is concerned about tears, even small ones, to the reinforced carbon covering the leading edges of the wings and fissures in the thermal tiles because the heat of reentry can reach 3,000 degrees Fahrenheit in some places on the shuttle’s hull.

Atlantis delivered a new part of the station’s truss, or backbone, as well as a set of solar arrays for the starboard side of the station. It also delivered 1,660 pounds of water, 115 pounds of oxygen and a new crew member, Clay Anderson, to replace Sunita Williams, who spent the last six months on the station.

The 10 astronauts and cosmonauts aboard the shuttle and station got a scare last week, when two Russian computers shut down during the installation of the solar arrays.

Experts in Russia and the United States mounted a crash effort to fix the computers, which control the orientation of the station and oxygen generation on the Russian side.

The Russians were finally able to restart the computers by bypassing a switch that protected the computers against a power surge. Although NASA turned off systems on the shuttle to allow the spacecraft to stay an extra day to help stabilize the station, the computers were working well enough by the weekend that controllers decided to allow Atlantis to undock and head home.

Officials said they had not found the “smoking gun” behind the outage. Russian experts are continuing to research the incident so they can bring the surge protection function back on line.

Station managers said Tuesday that with the installation of the new solar arrays the station is now slightly more than half-built. NASA is facing a 2010 deadline to finish construction, because the aging shuttle fleet is scheduled for retirement that year.

The next launch is scheduled for August.

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john.johnson@latimes.com