HOUSTON — Astronauts on the international space station Monday flexed some of the muscles on a robotic arm attached to a new Japanese lab they delivered and helped install on the orbiting outpost.

The $1 billion lab's robotic arm got its first thorough checkout during a two-hour procedure where it was fully extended, and all six of its joints were moved. The 33-foot robotic arm was first moved on Saturday, but only very slightly.

"It was such a pretty view, we just wanted to share it with you guys," Japanese astronaut Akihiko Hoshide told flight controllers near Tokyo as he operated the arm. The view from a video camera on the station showed the arm extended with the bright blue Earth in the background.

"Great job," Japanese flight controllers said after the testing was successfully completed.

At the end of the test, the arm was folded up and stored, out of the way of the lab's windows.

Over the summer, the station's crew will continue checking out the arm. This will culminate with the arm being used to grapple a storage shed that sits atop the lab.

The robotic arm won't be used for any actual work until after the launch into orbit next year of the lab's third and final section — a "porch" for exterior experiments — and a second, smaller robotic arm.

The 37-foot lab, named Kibo, Japanese for hope, was delivered by the shuttle and installed on the space station last week. The bus-size lab is the biggest room at the space station.

Later on Monday, astronauts planned to open up Kibo's storage shed, which has been sealed up since it was moved last week from a different location on the station to the lab.

The lab's shed — essentially a 14-foot closet or attic — was delivered to the station by another shuttle crew in March.

Astronauts were going to remove some equipment in the shed that is needed in other sections of the space station.

Emily Nelson, a space station flight director, said the shed will provide something that is often in short supply at the orbiting outpost.

"If you can imagine how full your house gets with stuff as you go through your life. But you can never have a garage sale and very infrequently can you take anything away. We have that problem on station," she said. "This will provide much needed storage space."

On Sunday, astronauts Michael Fossum and Ronald Garan Jr. completed the shuttle mission's third and final spacewalk on the orbiting outpost, replacing an empty gas tank and collecting a sample of dusty debris from a solar power wing's rotating joint. NASA is hoping the debris will give it clues about why another joint is malfunctioning.

Discovery and its crew are scheduled to leave the station on Wednesday.