NASA managers were still evaluating Atlantis' heat shield Wednesday, a day before the space shuttle was planned to land in Florida where a forecast for thunderstorms appeared to be the main obstacle for its return. The shuttle's first landing opportunity at 1:55 p.m., EDT, on Thursday, had thunderstorms predicted to be within 34 miles of the landing strip at Kennedy Space Center and clouds within 8,000 feet, both violations of flight rules.
NASA managers also were evaluating two technical issues before signing off on the landing. The first issue dealt with material known as gap filler, which appeared to be sticking out of a wing. Engineers wanted to make sure it could withstand the heat and aerodynamics of re-entry.
The second was a thermal blanket, which had peeled back during the June 8 launch and was repaired during a spacewalk last week. Engineers had initially made a mistake about how hot the thermal blanket could get during re-entry and wanted to recheck the data, said mission management team chairman John Shannon.
Despite the two unresolved issues, plans still were being made for landing on Thursday.
"The engineering and safety teams believe there is no risk at all during re-entry," Shannon said.
Atlantis commander Rick Sturckow told Mission Control in Houston that the weather looked fine to him as the shuttle flew 214 miles above the state.
"We're glad to hear the weather looks good from there," Mission Control responded. "We'll continue to watch it over the next 24 hours."
Atlantis has seven opportunities to land over four days.
Mission Control said landing opportunities at Kennedy, the primary landing site, look slightly better on Friday and Saturday. A backup landing site in California would be considered on Friday. That backup site plus another in New Mexico would be activated Saturday if necessary.
Atlantis has enough power for its systems to orbit until Sunday, but managers want the shuttle to land by Saturday. The flight would only be extended to Sunday if there were technical problems that needed to be fixed.
During the crew's 13-day mission to the international space station, the astronauts installed a new truss segment, unfurled a new pair of power-generating solar arrays and activated a rotating joint that allows the new solar arrays to track the sun.
The mission was extended by two days to give them time to repair the thermal blanket on the shuttle that peeled back during lift off. Astronauts Danny Olivas stapled down the blanket with a medical stapler during a spacewalk. Sturckow said he was confident the repair job would hold up.
"Everything looks great," he said Wednesday in an interview with reporters on the ground.
During their stay, Russian computers, which control orientation and oxygen production, crashed but they were revived several days later after cosmonauts Fyodor Yurchikhin and Oleg Kotov used a cable to bypass a circuit board. While docked to the station, astronauts conserved the shuttle's power in case they needed to spend an extra day at the outpost.
"When we left, they had the computers up and running," said Sunita "Suni" Williams, who was returning on Atlantis after spending more than six months at the space station. "I think there are some fixes they are going to need to do, but the station is fine right now. It's back to its normal condition."
Like any polite houseguests, Atlantis' astronauts did their best to clean up after themselves and followed the instructions of their hosts in Mission Control before landing.
"The dirty towels can be put in a laundry bag and stowed in the airlock," Mission Control wrote in instructions sent to the crew.
While Sturckow got a haircut from Yurchikhin before leaving the space station, Williams said a haircut was the one of the many things she was looking forward to back on the ground. Williams, whose nest of raven tresses defied gravity at the space station, set the record for longest single spaceflight by a woman.
"I'm looking forward to going to the beach and hopefully taking a walk with my husband and my dog on the beach," she said. "I can't wait for a good piece of pizza."
Associated Press writer Juan Lozano contributed to this report.