Two astronauts from the space shuttle Endeavour began their fourth and final space walk on Saturday, as meanwhile the US space agency NASA pondered a possible early return for the shuttle due to hurricane Dean, DPA reported. NASA previously had ordered the final space walk to be cut short by two hours in order to give the shuttle crew extra time to start preparing for a possible return to earth a day earlier than previously scheduled. Astronaut Dave Williams and space station flight engineer Clay Anderson during their space walk were to to install and remove antennas on the outside of the ISS and conduct other construction projects outside the spacecraft. Earlier Saturday, NASA officials said hurricane Dean might force the agency to cut the mission short by a day. Officials were keeping a wary eye on the path of the hurricane and the possibility that the flight control centre in Houston, Texas might have to be evacuated. The Endeavour is scheduled to undock from the International Space Station ISS on Monday and land at the Kennedy Space Centre in Florida on Wednesday. But now NASA was exploring the possibility that the shuttle would have to land a day sooner, on Tuesday, officials said. The last space walk came after NASA decided against repairing damage the shuttle sustained during takeoff. Commander Scott Kelly said Friday in a news conference from space that the crew agreed with the decision reached by NASA late Thursday not to repair a gash in the underside of the shuttle. NASA had been considering a repair for most of the week, before deciding that the repair was not necessary and the damage posed no threat to the astronauts' safety. Kelly said the crew was concerned that a repair could have dealt more damage to the orbiter. The damage was judged to be not serious enough to risk a catastrophic failure of the shuttle's heat shield, like the one that destroyed the shuttle Columbia on re-entry in February 2002, NASA officials said. The process of underside repairs during a spacewalk would have entailed risks for the astronauts during the process.
