The U.S. space agency NASA has announced a two-day extension to the mission of the Space Shuttle Atlantis to give its astronauts time to repair a problem with the orbiter's heat shielding.
John Shannon, the chair of the Atlantis mission management team, says engineers are working to decide the best method to repair a gap between a thermal blanket and the airframe of the shuttle's tail section.
The gap opened during Atlantis's climb to orbit on Friday. Shannon said late Monday that engineers decided the gap should be corrected before the shuttle reenters the Earth's atmosphere for landing.
Damage to heat shield tiles caused the Space Shuttle Columbia to disintegrate as it returned to Earth four years ago, killing all seven crewmembers.
Shannon said the repair to Atlantis might require a fourth spacewalk.
As he spoke, astronauts were making the first of the three spacewalks previously scheduled for Atlantis's visit to the International Space Station.
Astronauts Jim Reilly and John "Danny" Olivas floated outside the space station Monday on a 6.5-hour job to take off locks and remove bolts from a new set of solar panels. The panels will increase electrical power to the space station.