The head of the U.S. space agency, NASA, has pronounced the now-complete mission of the space shuttle Atlantis a great success.
NASA Administrator Michael Griffin told reporters the International Space Station is now halfway complete. He added he believes it will be finished on schedule.
Atlantis made a pre-dawn landing today at the Kennedy Space Center in Florida.
NASA has been under pressure to finish building the space station before the shuttle fleet is retired in 2010.
During its mission, the Atlantis crew completed three challenging spacewalks to install a pair of power-generating solar panels on the space station.
Several pieces of debris were lost during the mission, but NASA officials said those losses did not put the shuttle in danger.
It was the first construction mission since shuttle flights were grounded in 2003 after the Columbia catastrophe, when another space shuttle broke apart as it was re-entering Earth's atmosphere, killing all seven astronauts on board.