If weather prevents a return to Kennedy Friday, the backup landing site at Edwards Air Force Base in California will be activated Saturday for consideration as well.

Endeavour blast off July 15 from Kennedy Space Centre after five delays, on a trip to the space station. Its mission featured five spacewalks and completed construction of the Japan Aerospace Exploration Agency's Kibo laboratory.

Astronauts also replaced six batteries for the ISS and performed a number of other tasks, including tying down some cables and installing handrails and a portable foot restraint to aid future spacewalkers.

Seven more shuttle flights are planned over the coming year to complete the construction of the ISS. The launch of the next shuttle, Discovery, to the ISS is scheduled for the end of next month.