CAPE CANAVERAL, Florida NASA managers on Monday declared shuttle Endeavour safe to return to Earth, with touchdown targeted for Tuesday at the Kennedy Space Center in Florida.
The clearance followed a third and final in-flight inspection of the ship's heat shield, which the Endeavour crew scanned with a boom-mounted lasers and cameras after departing the International Space Station on Sunday following a nine-day construction mission.
Analysis of imagery collected during the inspection showed no areas of concern. Astronaut Chris Ferguson at Mission Control in Houston told the crew Endeavour was cleared for re-entry.
Landing is scheduled for 12:32 p.m. EDT (5:32 p.m. British time).
NASA clipped a day off of Endeavour's planned 14-day flight when it appeared Hurricane Dean could force evacuation of the Houston control center.
The monster storm instead was predicted to blast Mexico's Yucatan Peninsula with 150 mph (240 kph) winds, before cutting across the Gulf of Mexico and slamming into Mexico's central coast.
"Hurricane Dean is trending away (from Houston), so we don't think that's going to be a factor," Ferguson told Endeavour commander Scott Kelly.
"The weather at the Cape is looking pretty good," he said.
Nevertheless, NASA is staffing a backup landing site in California in case the forecast for Florida worsens.
Astronauts aboard the shuttle on Monday packed gear and checked the ship's landing systems. Kelly and pilot Charles Hobaugh used a computerized flight simulator to refresh themselves on landing manoeuvres after nearly two weeks in orbit.
The shuttle is returning with a small tear in its heat shield, caused when a piece of foam insulation broke off its fuel tank during launch on August 8 and smashed into the ship's underside.
After six days of evaluations and tests, NASA determined the 3-inch (8 cm) gash posed no threat to the crew or the shuttle and decided in-flight repairs were not needed.
The crew completed four spacewalks to install a new beam to the station's external backbone, replaced a failed gyroscope, which is used to keep the outpost properly positioned without chemical rocket firings, and prepared the complex for its first new modules in six years.
Astronauts are scheduled to deliver and install a connecting hub named Harmony during NASA's next shuttle mission scheduled for October. But before that can happen, managers need to determine if more modifications to the fuel tanks are needed to prevent insulation from flying off during launch.
A chunk of foam debris hit the shuttle Columbia during launch and damaged its left wing. NASA did not suspect or look for any damage and the shuttle broke apart as it flew through the atmosphere for landing on February 1, 2003, killing the seven astronauts aboard.
Endeavour's crew includes astronaut Barbara Morgan, a former teacher who originally trained to fly in 1985 as the backup to Christa McAuliffe, a teacher who flew on the ill-fated Challenger mission in January 1986.
Morgan became an astronaut to fulfil McAuliffe's goal of spotlighting educational opportunities during space flight. She plans to use her experience in orbit to develop activities and curricula for classroom teachers.
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