Mission Control, Houston has given the STS-118 crew a “Go” for undocking space shuttle Endeavour from the International Space Station at 8 a.m. EDT Sunday. The shuttle is scheduled to land Tuesday at NASA's Kennedy Space Centre on Cape Canaveral, Florida. The shuttle was previously scheduled to undock Monday from the ISS and to arrive on Wednesday in Florida.

The decision was made as astronauts Dave Williams and Clay Anderson were wrapping up the fourth spacewalk of the mission. Their spacewalk was reduced with two hours in order to allow the early hatch closing and departure.

Despite the shorter time outside the spacecraft Dave Williams and Clay Anderson installed a stand for the shuttle’s robotic arm extension boom on the station’s truss structure, an External Wireless Instrumentation System antenna and retrieved two containers of the Materials ISS Experiment.

By successful completing the last spacewalk Williams and Anderson had bumped up the total time for STS-118’s four spacewalks to 23 hours and 15 minutes. Saturday's excursion was the 92nd spacewalk devoted to station assembly.

Also, with this spacewalk the Canadian astronaut Dave Williams has reached to 17 hours and 47 minutes spent in space and he broke Chris Hatfield's Canadian record of just over 14 hours, set in 2001.

The National Hurricane Center said early Saturday that hurricane Dean was developing into an "extremely dangerous" category four storm as it heads toward the Yucatan peninsula in Mexico.
Winds were gusting at 240 kilometres per hour, putting it at the upper range of category four, and meteorologists said in broadcast reports it could jump to category five as it picks up strength over the warm Gulf of Mexico waters.

Leroy Cain, management team chairman, said NASA could not take the chance it would turn north and force the evacuation of Johnson Space Center in Houston.

"It would have been irresponsible for us not to take seriously this storm. It's a big storm and it's a serious storm," he said. "We're trying to put ourselves in a posture to be able to get out of harm's way, with the people and the assets, in the event we get unlucky," said Cain.

Also NASA warned that landing could be postponed to as late as Thursday if weather is bad at Kennedy or at alternative landing sites in California and New Mexico.

Late Thursday NASA mission managers in Houston decided not to repair the space shuttle Endeavour’s heat shield.

"After hours of reviewing data and imagery collected during the inspections by the (shuttle) crew, the managers decided the damage did not pose a safety risk to the crew or Endeavour," a NASA statement said.

The damage is not 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, but the process of underside repairs during a spacewalk would have entailed risks for the astronauts.

The crew of the Space Shuttle Endeavour said it agrees with NASA decision not to repair damage the shuttle sustained during takeoff.

"We're certainly concerned that if we did the repair we could do more damage to the underside of the orbiter," Commander Scott Kelly said. "The shuttle crew and the staging crew agreed with the decision not to the repair."