Discovery on Thursday docked with the International Space Station (ISS) to deliver a German astronaut for a six-month stay and assist with repairs to the structure orbiting 400 km above the earth.
The arrival of German Thomas Reiter, 48, marks the first time since the 2003 Columbia disaster that three astronauts have occupied the ISS.
The crews on the shuttle and space station will wait about two hours before opening the doors to greet each other.
Before docking, Discovery flipped over so that its underbelly could be photographed by the space station crew to check for any damage to the craft's heat shielding tiles.
It was the second inspection since Discovery's launch on Tuesday.
NASA examined the shuttle's exterior with lasers and cameras Wednesday as part of a routine procedure introduced after the Columbia tragedy, which was blamed on a large piece of foam that fell off the external fuel tanks and damaged the shuttle's protective tiles.
Columbia burned up while re-entering the earth's atmosphere.
The problems continue to dog NASA scientists and engineers. Several small pieces of foam fell from Discovery's fuel tank during liftoff, but NASA believes it can closely monitor the situation under the new safety rules enacted after Columbia.
Discovery is to remain docked at the ISS until July 14, and is scheduled to return to Earth on July 16, landing at Cape Canaveral, Florida.