"The TPS (thermal protection system) is 100 per cent clear for entry," a mission control official told Discovery commander Steven Lindsey from the Johnson Space Center in Houston, Texas on Saturday.
"That is great news. That's fantastic," Lindsey, who docked Discovery to the International Space Station (ISS) on Thursday, replied.
The shuttle is scheduled to return to Earth on July 17.
Analysts spent the last few days poring over a mountain of images to look for any potential damage caused by debris during Tuesday's liftoff from Cape Canaveral, Florida.
But they concluded that astronauts would not need to conduct a spacewalk to repair the shuttle.
Discovery will get the final all-clear to land after a last checkup at the end of the mission to make sure it was not hit by micrometeorites while in orbit.
Sixteen nations are sponsoring the $100 billion outpost, which is only half built and will require another 16 space shuttle flights to complete.
The $100 billion space station is
only half-built, as yet
Reiter represents the European Space Agency, which is counting on having its Columbus space laboratory module coupled up with the space station after a planned launch next year.
"We are all waiting desperately for the launch of our module," Reiter said.
Space station construction has been on hold since the 2003 disaster involving the shuttle Columbia. The shuttle broke apart as it descended toward Florida on Feb. 1, 2003 because of a hole punched in its wing heat shield at launch by insulating foam that shook loose from the external fuel tank.
Hot gases entered the breach during its fiery descent through the atmosphere, which destroyed the spacecraft and killed the seven astronauts on board.
More foam came loose during Discovery's liftoff on the first post-Columbia flight last summer and on its Fourth of July blastoff last week.
'A clean vehicle'
But while analysis of launch video and other data was still underway on Sunday, Nasa managers said Discovery's fuel tank performed substantially better than any flown on the shuttle since flights began 25 years ago.
Discovery shuttles have undergone
safety upgrade after 2003 disaster
"This was the best, cleanest orbiter I've ever seen," said Steve Poulos, orbiter project manager at the Johnson Space Center in Houston.
"I'm very confident that we'll have a clean vehicle to return on," added rookie flier Stephanie Wilson, speaking during the in-flight news conference.
A steady stream of good news about Discovery's condition has given Nasa growing confidence that its $1.3 billion safety upgrade of the shuttles following the Columbia disaster is a success.
Discovery's flight was viewed by many in the US space agency as a make-or-break mission for the troubled shuttle programme, which must complete assembly of the station before the three-ship fleet is retired in 2010.
Latest Discovery flight was seen
as a make-or-break mission
One lingering concern focuses on a couple of ceramic cloth "gap fillers" sticking out from between heat shield tiles. Nasa managers said one had been judged safe and the other was under study but was expected to be cleared on final analysis.
The same was true for minor damage to protective thermal blankets on the spacecraft.
If it turns out there is a significant problem, astronauts Piers Sellers and Michael Fossum could attempt to fix it while spacewalking ahead of landing on July 17.
The Discovery crew spent their first few days in space scanning their ship's heat shield for damage. On Saturday, Sellers and Fossum tested the stability of a 100-foot (30-metre) boom that could be used to position future crews anywhere on the outside surface of the shuttle for possible repairs.
The test was "successful," said Sellers. "The boom can be used as a work platform."