US: The Discovery astronauts were completing an intricate inspection of the space shuttle's vulnerable heat shield last night to back up Nasa's initial assessment that the Independence Day launch caused no significant damage.
Mission managers said pieces of foam seen coming off the spacecraft during its ascent to orbit were too small and came too late in the flight to cause any ruptures in the reinforced tiles that protect the crew from the intense heat of re-entry.
"We saw nothing that gives us any kind of concern about the health of the crew or the vehicle," Wayne Hale, Nasa's shuttle programme manager, said.
During yesterday's six-hour inspection a camera on the end of the shuttle's robotic arm sent back clear images of the tiles on the sensitive nose cone and wing edges where Columbia was struck by falling debris in 2003, leading to its destruction and the death of seven astronauts.
The only unusual thing found initially was a whitish splotch on Discovery's right wing that looked like a bird dropping. There was one on the wing a few weeks ago at the launch pad, flight director Tony Ceccacci said.
Mr Ceccacci said the imagery experts would study the splotch and make sure it was nothing more than a bird's signature.
Although managers warn that it will be several days into Discovery's 13-day mission to the International Space Station before the agency can study all the data and give the orbiter a clean bill of health, they remain confident.
"The foam pieces we saw were all very minor and all very late, coming after the two-minute, 15-second 'bingo' time when they are aerodynamically no longer a threat," Mr Hale said.
A stretch of "fabric" that mission specialist Michael Fossum filmed from the cockpit during the eight-minute ride into space was identified as harmless ice from the fuel tank's nose cone.
British-born astronaut Piers Sellers, who will make the first of three spacewalks on Saturday to test safety improvements since the Columbia disaster, reported that onboard systems were performing well. "We have all the computers up and they're singing nicely."