Astronauts aboard the US space shuttle Endeavour prepared on Thursday to inspect the heat shield for damage caused by debris that peeled off the external fuel tank during liftoff.
The debris was spotted after the shuttle blasted off Wednesday from the Kennedy Space Center, its sixth bid in recent weeks to reach the International Space Station after delays caused by weather woes and technical glitches.
The six Americans and one Canadian aboard Endeavour are scheduled to reach the ISS on Friday, where they will complete the Japanese Kibo laboratory, a platform for astronauts to conduct experiments 350 kilometers (220 miles) above Earth's surface.
A US space agency official downplayed the potential of damage caused by the debris that could be seen hitting the shuttle about two minutes into the flight in images broadcast on NASA TV.
The debris could be ice or foam that broke off from the external fuel tank, said Bill Gerstenmaier, NASA associate administrator for space operations.
"We had some foam loss events," Gerstenmaier told reporters. "You can clearly see, on the front part of the orbiter, some white indications where the tiles were dinged.
"We don't consider those an issue for us, those are probably coating losses," he said. But specialists will scrutinize the images, Gerstenmaier said.
NASA piped in the song "These Are Days" by the band 10,000 Maniacs for the Endeavour's crew wake-up, "targeted especially for Mission Specialist Tim Kopra," the space agency said.
Commander Mark Polansky and pilot Doug Hurley were to kick off the day's work with an Orbital Maneuvering System engine firing to fine-tune Endeavour?s path toward the ISS. Officials plan a second burn at the end of the crew?s day.
The crew also will install a camera in the shuttle's docking tunnel, extend the Orbiter Docking System ring and check out the hand-held laser range-finder and other equipment ahead of docking.
For the heat shield inspection, specialists Chris Cassidy, Tom Marshburn, Dave Wolf, Kopra and Julie Payette of the Canadian Space Agency would use Endeavour's robotic arm and the Orbiter Boom Sensor System, NASA said.
And Wolf, Cassidy, Marshburn and Kopra also were to begin sizing up space suits they will wear and the tools they will use on the mission?s five spacewalks.
The Endeavour mission aims to help fulfill "Japan's hope for an out-of-this-world space laboratory," as the shuttle delivers state-of-the-art equipment to conduct experiments in the vacuum of space, the US space agency has said.
NASA has been cautious about conditions for the space shuttle's exit and return since the shuttle Columbia blew apart some 20,000 meters (65,500 feet) above the Earth in 2003 as it
was returning from a 16-day space mission to land in Florida.
A chunk of insulation that broke off from the shuttle's external fuel tank during takeoff had gouged Columbia's left wing heat shield, allowing superheated gases to melt the shuttle's internal structure before it exploded, killing all seven astronauts onboard.
The ISS should be completed in 2010, also the target date for the retirement of the US fleet of three space shuttles.