Huge new solar wings have been unfurled on the International Space Station.
The wings were deployed in stages to allow them to warm
The new arrays, which are 73m (240ft) long and have a width of 11.5m (38ft), will double the amount of power available to the orbiting outpost.
They are attached to the platform's P3/P4 truss, a new "backbone" segment fitted to the ISS this week by astronauts from the Atlantis shuttle.
The astronauts will conduct a third and final spacewalk on Friday to prepare the structure for full operation.
The ISS will eventually have 11 integrated truss segments that stretch 108m (356ft) from end to end.
They will support four virtually identical solar array assemblies. They will also support radiators that will cool the station.
The Atlantis shuttle is expected to leave the ISS on Sunday. It needs to be clear of the platform to allow a Russian Soyuz rocket, carrying a new ISS crew and the first female space tourist, to dock during the middle of next week.
Atlantis' mission to the station is only the third shuttle flight since the orbiter Columbia broke up on re-entry after being damaged by launch debris in 2003.
Nasa plans at least 14 more construction missions to the space station over the next four years and must complete assembly before the orbiter fleet is retired in 2010.