Canadian astronaut Dave Williams says he isn't worried that Endeavour will return to Earth with a gouge in its belly, after NASA chose not to fix the damage in orbit.
"I think they've made the right decision," Williams said Friday from the International Space Station.
"Going beneath the surface of the orbiter to repair the tile is something that has its own risks. So we're balancing those. I think we're going to be fine on entry."
If NASA had decided otherwise, Williams and another astronaut would have been tasked with covering up the gouge.
"There is certainly more risk in doing the repair than we're willing to take. ... We were certainly concerned that if we did the repair that we could potentially cause more damage to the underside of the orbiter," said Endeavour commander Scott Kelly.
"Since a repair was not really warranted, based on the data and the testing ... the shuttle crew and the station crew actually agreed with the decision not to do the repair."
The decision to forgo the repair came after several days of testing, analysis and deliberation.
Mission managers decided they couldn't justify putting astronauts at risk if the shuttle was in a satisfactory condition that would get them home.
The massive amount of data gathered from hundreds of engineers indicated Endeavour would suffer no serious structural damage during next week's re-entry.
There had been concerns that the heat of re-entry could weaken the shuttle's aluminum frame at gouge, thus resulting in extensive post-flight repairs. But tests showed this would not be the case.
A piece of debris that broke off the external fuel tank shortly after liftoff on Aug. 8 pierced the thermal shielding on Endeavour's belly.
The debris carved out a 9-centimetre-long, 5-centimetre-wide gouge and burrowed its way through the thermal tiles.
Left completely uncovered was a narrow two-and-a-half-centimetre strip of the overlying felt fabric, which served as the last barrier before the shuttle's aluminum structure.
The only way they could have fixed the gouge was by positioning Williams and another crewmember, armed with black protective paint and caulk-like goo, beneath the shuttle on the end of a 100-foot robotic arm and extension boom.
The astronauts have already successfully completed their main tasks, including fixing a new truss segment to the station and replacing a gyroscope that helps control the station's orientation.
Williams is to perform the fourth and final spacewalk of the mission on Saturday.
On Friday, he described the experience, thus far, as "an amazingly smooth experience."
"The view is very, very hard to describe. Just imagine yourself standing on a platform, you really can't see your feet at all but all around you you've got this panoramic view of the earth beneath you," he told reporters.
"It's absolutely spectacular and it was kind of sad when we transitioned from a day pass to a night pass because we lost the view and had to go back to looking at what we were doing."
Once Williams goes on his third spacewalk, he will have set a Canadian record for the number of spacewalks and hours spent outside the International Space Station.
