Indian-American astronaut Sunita Williams and her Japanese colleague on board the International Space Station on Thursday ventured outside the lab to perform maintenance tasks of their home in orbit.
Nasa Flight Engineer Williams and Japan Aerospace Exploration Agency Flight Engineer Akihiko Hoshide aim to replace a faulty power-switching unit and a failing robotic arm camera of the International Space Station.
This is the fifth spacewalk undertaken by 46-year-old Williams.
On August 20, two Russian astronauts worked outside the orbiting lab to relocate a cargo boom.
But Thursday's spacewalk is the first performed by a US astronaut since the final shuttle mission in July 2011, floridatoday.com reported.
Williams along with Hoshide and Yuri Malenchenko of Russia left for the ISS aboard a Russian spacecraft Soyuz TMA-05M on July 15 from the Baikonur cosmodrome in Kazakhstan.
Williams, who was a flight engineer on the station's Expedition 32 crew, became commander of Expedition 33 after reaching the space station.
Williams was selected as an astronaut candidate by Nasa in 1998. She was assigned to the International Space Station as a member of Expedition 14 and then joined Expedition 15.
She holds the record of the longest spaceflight (195 days) for female space travellers.