Two NASA astronauts have set out on a spacewalk to carry out repairs at the International Space Station (ISS).
Part of the ISS cooling system automatically shut down last week after detecting abnormal temperatures.
While NASA says the ISS crew are not in danger. But the partially-running cooling system is not enough to keep supporting all the laboratories on the US side of the station, so needs to be fixed.
On the first of three planned spacewalks to rectify the problem, American astronauts Rick Mastracchio and Mike Hopkins are due to disconnect a pump containing a faulty valve.