Space shuttle Discovery has safely touched down at NASA's Kennedy Space Center in Florida.
The craft began its descent at 10:10 a.m. ET after getting the go-ahead from Mission Control.
Sixty-five minutes later, the craft glided through the clear blue skies above Florida and made a textbook landing.
Asked if it was a perfect mission, astrophysicist Wanda Le Claire told 麻豆影视net: "It was pretty close. They were able fulfil all of the mission requirements, get everything done that they needed to get done, as well as the additional toilet repair."
The US$100-billion International Space Station's lone toilet broke down two weeks ago, forcing astronauts to carry out manual flushes with scarce water several times per day.
Discovery brought up replacement parts when it docked on June 2.
On Friday, NASA engineers said a broken metal clip on Discovery's rudder posed no threat to the spacecraft's return. The clip is only important during lift-off.
Discovery blasted skyward on May 31, taking Kibo, Japan's US$1-billion lab, to the space station about 400 kilometres above Earth, arriving two days later.
The new module will allow astronauts to carry out experiments in space, Le Claire said.
"That's a bit of a new thing. This will allow them to expose stuff to the vacuum of space, allow it to be bombarded by the radiation of space," she said.
The manipulator arm for experiments on the Kibo (Japanese for "hope") module will mean astronauts won't have to go on risky spacewalks and be exposed to that radiation themselves, she said.
Montreal-born U.S. astronaut Gregory Chamitoff stayed behind at the space station for a six-month stint.
U.S. astronaut Garrett Reisman returned to Earth with Discovery after a three-month stay at the station.
Le Claire said mission specialists get replaced when their work is done.
With files from The Associated Press
