CAPE CANAVERAL, Fla. – Atlantis' heat shield is safe enough for the shuttle to return to Earth, mission managers decided Wednesday, a day before the space shuttle was scheduled to land in Florida. A forecast for thunderstorms appeared to be the main obstacle for its return.
For the shuttle's first landing opportunity at 1:55 p.m. EDT on Thursday, thunderstorms were 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.
Before signing off on the landing, mission managers held an unusual, last-minute meeting to clear up three remaining technical issues. Material known as gap filler appeared to be sticking out of a wing, a thermal blanket had peeled back during the June 8 launch and debris was found floating after Atlantis undocked from the international space station on Tuesday.
Engineers had wanted to make sure the gap filler could withstand the heat and aerodynamics of re-entry and recheck data on the thermal blanket, which was repaired during a spacewalk last week. Mission managers have said the debris may have been ice.
"We were just trying to be completely thorough," said mission management team chairman John Shannon. "The engineering and safety teams believe there is no risk at all during re-entry."
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 trusses 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."