U.S. astronauts finish maintenance of space station

Astronaut Danny Olivas works outside the International Space Station during his spacewalk in this image from NASA TV September 5, 2009. Olivas and fellow spacewalker European Space Agency astronaut Christer Fuglesang are working to deploy a cargo attachment system and to replace a device designed to help the station determine its position relative to the Earth. (Reuters Photo)

European Space Agency astronaut Christer Fuglesang (L) and astronaut Danny Olivas (Top) work outside the International Space Station during their spacewalk in this image from NASA TV September 5, 2009. Olivas and Fuglesang are working to deploy a cargo attachment system and to replace a device designed to help the station determine its position relative to the Earth. (Reuters Photo)

European Space Agency astronaut Christer Fuglesang exits the airlock in this image from NASA TV September 5, 2009. Fuglesang and fellow spacewalker Danny Olivas scheduled extravehicular activities include the outfitting and maintenance of the International Space Station modules. (Reuters Photo)

European Space Agency astronaut Christer Fuglesang works outside the International Space Station's Qwest airlock in this image from NASA TV September 5, 2009. Fuglesang and fellow spacewalker Danny Olivas are working to deploy a cargo attachment system and to replace a device designed to help the station determine its position relative to the Earth. (Reuters Photo)

WASHINGTON, Sept. 5 (Xinhua) -- Two U.S. astronauts conducted a third and final space walk for shuttle Discovery's STS-128 mission on Saturday and finished outfitting and maintenance of International Space Station modules, NASA said.

According to NASA, Discovery's mission specialists Danny Olivasand Christer Fuglesang began the space walk at 4:39 p.m. EDT (2039 GMT), which lasted over seven hours.

The duo deployed a payload attachment system on the starboard truss and replaced a failed rate gyro assembly, which measures rates for any changes in the station's attitude, with a new one.

With that complete, they split up for the next tasks. Olivas installed a Global Positioning System antenna while Fuglesang replaced a remote power control module and installed an insulation sleeve on a cable inside the truss. Fuglesang followed that up with the installation of a second GPS antenna.

The two then reunited for the final task, routing 60-foot-long avionics systems cables along the station. The cables are being installed in preparation for the arrival of the Node 3 "Tranquility" in 2010.

Discovery lifts off midnight on August 28 from the Kennedy Space Center in Florida after two delays. Its 13-day flight is scheduled to end with a landing back in Florida on Thursday.