Space shuttle Endeavour has launched on a mission to finish construction of a new science lab at the International Space Station.
The seven astronauts aboard Endeavour began their journey Wednesday evening to deliver the third and final segment of the Japanese Kibo science laboratory. NASA commentator Mike Curie counted down to the liftoff from Kennedy Space Center in Florida.
"We have main engine start, and four, three, two, one. Booster ignition and liftoff of Endeavour, completing Kibo and fulfilling Japan's hope for an out-of-this-world space laboratory," he said.
The Endeavour was supposed to launch last month, but a hydrogen leak forced officials to postpone while technicians fixed the problem. A series of thunderstorms caused further delays this week.
The Endeavour crew will spend nearly two weeks at the station to install the Kibo lab and perform other maintenance tasks, such as swapping out batteries in the station. The Kibo module will expand work space on the station and allow astronauts to conduct experiments that involve exposing materials to the vacuum of space.
Astronaut Tim Copra will replace Japanese astronaut Koichi Wakata, who has been living aboard the station since March.
While the shuttle is docked to the station, there will be 13 astronauts working in space at one time - the highest number in the station's history.
After Endeavour returns to Earth, only seven shuttle missions will remain before NASA plans to retire the fleet next year.