Live in orbit: Astronauts move station rail carts

Riding on the end of the International Space Station's Canadian-built construction arm, U.S. flight engineer Clay Anderson hauled the second of two rail carts into position on the first starboard section of the outpost's central truss.

Endeavour mission specialist Rick Mastracchio positioned himself on the side of the aluminum girder, where he latched the cart down on rails that run atop the truss. The relocation of the carts was the second major task of a planned 6.5-hour spacewalk.

Mastracchio now will move over to the station's Z-1 truss and try to engage gimbal locks on a radio communications antenna. The locks did not align properly during a spacewalk last September.

Anderson is headed back to the P-6 truss to remove a radio transponder that no longer will be needed when the girder is mounted later this year on the far left end of the central truss.

The spacewalkers also aim to retrieve a pair of suitcase-sized materials science experiments from the exterior of the U.S. Quest airlock. The science packages will be stowed inside the Spacehab module in the shuttle's cargo bay and returned to Earth next week.

The astronauts are about an hour ahead of schedule.