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HOUSTON - The space shuttle Endeavour crew unpacked their ship's robot arm, latched on an extension to double its length and deployed it beneath the spaceship to image heat shield damage that occurred during their launch last week.
Nasa believes the damage is minor, but the US agency leaves little to chance since losing the shuttle Columbia crew in 2003 from a similar incident.
The shuttle's design allows some insulation from its fuel tank to rain down on the orbiter during launch.
"We don't think it (the debris impact) went all the way down to the bottom" of the tile, John Shannon, deputy shuttle program manager and head of the mission management team, told reporters late on Saturday.
"If we even have half the tile left, then we're not going to have any issues at all," he added.
The shuttle is covered with ceramic heat-resistant tiles and carbon panels to protect its aluminum skin from melting during the plunge back through the atmosphere for landing. Temperatures around the damage site can reach up to 2,000 degrees Fahrenheit (1,093 degrees Celsius).
Columbia disintegrated as it flew through the atmosphere for landing due to undetected damage caused by a piece of insulation that fell off the shuttle's external fuel tank during liftoff. All seven astronauts aboard were killed.
Nasa has twice redesigned the tank since the accident to minimize foam shedding and has one more fix in the works that will be ready next year. That should rectify an ongoing problem with foam falling off a bracket that holds an oxygen feed line to the outside of tank, which is where a grapefruit-sized chunk of foam that fell off Endeavour's tank came from.
Though managers believe the 3.5-inch (8.9-cm) gouge on the underside of Endeavour is not a safety hazard, they ordered an extra inspection to gather more information.
Teacher-turned-astronaut Barbara Morgan began the scan, which was expected to take about three hours, operating the 100-foot-long (30.5 metre) boom from a control station on Endeavour's flight deck.
The shuttle arrived at the International Space Station on Friday for a seven- to 10-day construction and resupply mission.
The scans by the shuttle's laser and high-resolution video cameras should yield a three-dimensional portrait of the damage caused by the chunk of foam that fell off Endeavour's fuel tank about a minute after liftoff from the Kennedy Space Center in central Florida on Wednesday.
Based on video and pictures taken during launch from shuttle- and ground-based cameras, engineers believe the foam, or chunks of it, skipped along the shuttle's smooth belly like a stone across water, leaving three more imprints before it was obliterated.
Morgan and crewmate Tracy Caldwell were to pass the shuttle's scanners over all the damage sites, as well as a piece of protruding insulation around the shuttle's main landing gear door.
Engineers will then determine if any repairs are needed before the shuttle is cleared to return to Earth.
Managers are expected to extend the shuttle's flight, originally scheduled for 11 days, to two weeks so the crew will have more time to prepare the $100 billion orbital outpost for the arrival of research laboratories later this year and in 2008. If any heat shield repairs are needed, the work will be added to one of the two or three remaining spacewalks.
If the mission is extended, Endeavour's return to the Kennedy Space Center would be on August 22.
- REUTERS
