Two astronauts from the US space shuttle Endeavour began the first spacewalk of their 13-day mission on Thursday, preparing to install a new node on the International Space Station.
NASA said Robert Behnken and Nicholas Patrick began their walk at 9:17 pm (0217 GMT Thursday), leaving the decompression chamber where they spent the night some eight minutes later than scheduled.
Over the course of the six-and-a-half-hour flight, the two spacewalkers will prepare for the installation of the new Tranquility node on the ISS, which comes attached with a seven-windowed dome observation deck that will provide spectacular panoramic views of Earth and space.
Behnken will begin by uncovering a camera that will be used to line-up two nodes during installation of Tranquility before removing eight contamination covers on the new module.
Patrick meanwhile will work to install an electric circuit on part of Tranquility and will also remove cables that allowed the node to be powered from the Endeavour.
Behnken, the lead spacewalker for the mission, is undertaking his fourth spacewalk, while Patrick is heading out for the first time.
Built for NASA by the European group Thales Alenia Space in their Turin factory, the paranomic views offered by the cupola attached to Tranquility will help crew members monitor space walks and docking operations. It can accommodate two crew members at a time, and is equipped with portable workstations that can control station and robotic activities. Six windows are arrayed along its sides and another on top -- all protected against the impact of tiny meteorites.
Once the new room is in place, the space station will be 90 percent complete.
The mission, one of five scheduled for NASA's three shuttles before the program ends later this year after a 29-year run, comes as the US space agency reevaluates its future after President Barack Obama effectively abandoned its plan to send astronauts back to the moon by 2020.
Constrained by soaring deficits, Obama submitted a budget to Congress that encourages NASA to focus instead on developing commercial transport alternatives to ferry astronauts to the ISS after the shuttle program ends.
The ISS, a joint project involving 16 countries, has cost around 100 billion dollars, mostly funded by the United States. Under Obama's new budget, the floating research station could see its life extended by five years until 2020.