WASHINGTON -- Astronauts who conducted spacewalk on Saturday accidentally inserted a pin upside down and jammed an equipment storage platform at the International Space Station, a NASA official said.

International Space Station flight engineer Yury Lonchakov (L) is seen with members of the Space Shuttle Discovery crew during hatch opening ceremonies aboard the station in this image from NASA TV March 17, 2009. The Discovery astronauts are (L-R) Joseph Acaba, Koichi Wakata of the Japan Aerospace Exploration Agency, Pilot Tony Antonelli, Steve Swanson, Richard Arnold, John Phillips and Shuttle Commander Lee Archambault. [Xinhua]

Astronaut Joseph Acaba installed the clamp like pin upside down -- "180 degrees out from where it should have been," said Glenda Laws-Brown, official in charge of spacewalk in NASA's Mission Control.

According to Laws-Brown, NASA has assembled a team of experts to determine whether there's any way the crew can pry or hammer the pin loose during a spacewalk Monday -- the third and final of shuttle Discovery's mission.

Astronauts Steven Swanson and Joseph Acaba finished the second of three planned spacewalks Saturday to make preparation for NASA's future space shuttle mission and the debut flight of a Japanese cargo ship.

The NASA TV shows that they exited the space station at around 0:51 p.m. EDT (1651 GMT) to start the outing, which lasted about six and half hours. It's Swanson's fourth spacewalk of in his career and Acaba's first.

During the spacewalk, they loosened connections on batteries on the external Port 6 truss, ready for their replacement on a later mission in June.

The two also installed a GPS antenna to the outside of the station's Japanese module. The GPS device will help guide the Japanese HTV robotic spacecraft, a cargo transfer vehicle to be put into operation later this year.

The autonomous craft will supply the station's Kibo laboratory with water, food and scientific materials, and could also resupply the rest of the station if needed.

Other tasks include outfitting the station's truss with attachments for experiments and cargo platforms and using an infrared camera to photograph radiator panels so engineers can assess how they have withstood the harsh space environment.

Two astronauts from Discovery's crew performed the first spacewalks Thursday and successfully installed the International Space Station's fourth and final set of solar array wings. Astronauts unfurled the solar wings Friday, bringing the 10-year-old space station to full power, which is critical for boosting science research and allowing the crew to double to six.

The space station's six solar wings already are in place. The new ones bring the number to eight, with four on each side.

Each solar array wing has two 115-foot-long (35 meters) arrays, for a total wing span of 240 feet (73 meters), including the equipment that connects the two wings and allows them to twist as they track the sun.

Altogether, the station's arrays can generate as much as 120 kilowatts of usable electricity -- enough to provide about forty-two 2,800-square-foot (260 square meters) homes with power.

One more spacewalk is planned next Monday during Discovery's mission.

Discovery was launched into space last Sunday night. During its stay with the station, three spacewalks will be conducted by astronauts. If all goes well, it is scheduled to undock from the station on March 25, towards a planned March 27 landing at the Kennedy Space Center in Florida.