WASHINGTON, September 14 (RIA Novosti) - The crew of the U.S. space shuttle Atlantis has completed the installation of new solar arrays at the International Space Station, a NASA spokesman said Thursday.

The spokesman told RIA Novosti the new arrays, which are 74 meters long and 12 meters wide, were placed on the new P3/P4 truss installed Tuesday.

The arrays are expected to double the station's power capability.

NASA's news service said the installation of the arrays was originally scheduled for May 2003, but was postponed following the Columbia disaster, which claimed the lives of seven astronauts in February of that year.

Astronauts Joe Tanner and Heide Stefanyshyn-Piper will perform their third and final spacewalk Friday to replace a number of communication devices. The spacewalk is expected to last 6.5 hours.

NASA ISS Program Manager Mike Sufferdini said the shuttle will undock from the station September 18 instead of September 19. He also said a new shuttle flight to the ISS could take place in December.

Atlantis, which was launched Saturday following two weeks of delays caused by storms and technical malfunctions, docked with the ISS at 2:48 p.m. Moscow time (10:48 a.m. GMT) Monday above the southeastern Pacific.