During a six and a half hour spacewalk, Joseph Acaba and Richard Arnold "repositioned an equipment cart from the Port 1 to Starboard 1 truss segment, installed a new coupler on the CETA cart, lubricated snares on the "B" end of the space station's robotic arm," but failed to fix a problem with a jammed cargo carrier system, tying it safely in place instead.
During the first spacewalk of the mission on Thursday, Swanson and Richard Arnold installed the last set of solar wings on the ISS to bring the total number of solar panels to eight.
The solar array will provide the electricity to fully power scientific experiments and support the station's expanded crew when it is increased to six in May.
During the second spacewalk late on Sunday, Swanson and Acaba installed a second Global Positioning Satellite antenna on the Japanese Kibo laboratory, as part of work to complete the orbital station.
However, they were unable to deploy the Port 3 unpressurized cargo carrier attachment system due to an unidentified problem, NASA said.
The Discovery lifted off from Florida's Cape Canaveral on Monday and docked with the ISS at 17:20 EDT on Wednesday (21:20 GMT Tuesday).
The shuttle delivered a crew of seven to the ISS, including Japanese Aerospace Exploration Agency astronaut Koichi Wakata, and also brought with it the space station's fourth and final set of solar panels.
Wakata, the ISS's first long-duration Japanese resident, replaced U.S. astronaut Sandra Magnus, who will return to Earth on Discovery after more than four months aboard the space station. The Japanese astronaut is scheduled to return to Earth during the next shuttle mission, STS-127, scheduled for June 2009.
NASA is planning to wrap up the current Discovery mission on March 25 and the shuttle is scheduled to land on March 28 at 13:42 EDT (17.42 GMT).
