The return of shuttle Atlantis, which will bring back Indian-American astronaut Sunita Williams home after her six month space sojourn has been delayed by two days to help astronauts fix a problem on the body of the spacecraft.
The decision to add a fourth space walk to the Atlantis crew's schedule to fix the thermal blanket on the shuttle's exterior will mean a mission of 13 days in space rather than the originally planned 11 days, said John Shannon, head of the mission management team at the National Aeronautics and Space Administration(NASA).
The announcement came even as two Atlantis astronauts ventured out for the first space walk of the mission on Monday.
The shuttle which blasted off last Friday was originally scheduled to return to earth on next Tuesday.
No decision had been made on whether the loosened blanket, covering a 4-inch by-6-inch area over a pod for engines, will be repaired during a previously planned third spacewalk or a fourth, extra one, officials said. NASA has however played down concerns over the damage to Atlantis.
The loosened blanket was discovered on Saturday during an inspection of the shuttle.
Engineers think that the blanket was loosened by aerodynamic forces during launch, not by being hit by a piece of debris during liftoff.
The rest of the vehicle appeared to be in fine shape, NASA said.
The shuttle -- on its first mission of the year -- docked with the ISS Sunday, after performing a dramatic backward somersault in space.