The U.S. space shuttle Discovery's astronauts have completed one repair of the orbiter, but mission controllers say the astronauts may have to make another repair before the shuttle returns to Earth next week.
The repair of the space shuttle was performed by American Steve Robinson.
Attached to a robotics arm, Mr. Robinson gently yanked two protruding pieces of filler fabric from between heat tiles on the underside of the orbiter.
Mission director Paul Hill had this reaction to how smoothly things went.
"I was absolutely relieved, and I think you could probably hear the sigh of relief throughout the building over there," he said. "And when he pulled the second one out, it was a huge relief. And it definitely felt like the rest is downhill from here."
The gap fillers protect the fragile heat tiles from knocking against each other during take off.
NASA engineers had worried that the fillers could alter the aerodynamic flow of hot gasses along the bottom of the shuttle during its reentry into Earth's atmosphere, causing a disaster similar to what happened in February 2003 to the space shuttle Columbia, which burned up upon reentry and killed all seven astronauts.
But the astronauts may have to make one more repair before the shuttle is cleared for landing next week. Mission managers are studying a billowing piece of thermal insulation fabric near the window on the commander's side of Discovery.
NASA officials say the fabric apparently came loose when it was hit by debris during take-off. They fear the blanket could fly off during reentry and strike the shuttle.
If engineers on the ground determine that another space walk is necessary, the repair could involve either snipping the fabric or shredding it into tiny pieces.
But Mr. Hill says mission controllers are carefully weighing the pros and cons before they conduct another repair mission.
"Sending somebody down by this window would take some amount of risk," he added. "Then [if] we put them up close to the orbiter we could do some amount of unintentional damage on the orbiter, and then pulling on this blanket, if we decide to do something like that, we could make a bad situation worse. So, we would have to think real hard about sending somebody out there and taking that risk."
Mr. Hill says the presence of dozens of cameras taking pictures of the Discovery during take off and in orbit helped NASA spot potentially serious damage to the space shuttle that not have been noticed in the past.