NASA astronauts completed the second of five spacewalks on Sunday, as they continued a demanding two-week mission to continue construction of the International Space Station (ISS).
The latest spacewalk started at 1502 IST (0932 GMT) and finished at 2135 IST (1605 GMT), with space shuttle Discovery astronauts Scott Parazynski and Daniel Tani removing bolts in preparation for the installation Tuesday of a truss that will support a set of the station's key solar panels.
The truss is the biggest piece of equipment yet to be moved around on the station on this latest mission to the ISS, during which the astronauts will perform a record five spacewalks totalling some 30 hours.
The ISS, a giant manned laboratory orbiting 390 kilometres above Earth, is aimed to be a potential jumping-off point for further exploration of the universe.
The 100-billion-dollar space station, supported by 16 countries, is considered key to US ambitions to send a manned mission to Mars and is due to be completed within three years.
Mission specialist Parazynski and Tani, a flight engineer, disconnected truss cables from the top of the station, where the assembly was installed temporarily in 2000.
Then the space station's robotic arm, operated by astronauts inside the ISS, moved it to an overnight parking position. It will be installed in a new spot on the ISS during further spacewalks over the coming days.
The spacewalkers will also complete the external outfitting of the Harmony module, a new compartment recently installed on the station. Tani is to inspect other equipment including a joint used to rotate the solar panels.