Today British astronaut Tim Peake did his first spacewalk.
The astronauts' spacewalk began at 12:48pm GMT today, and officially ended at 5:31pm after Kopra reported water inside his helmet.
Peake and Kopra completed their main task, which was to replace a power unit that failed in November.
The Sequential Shunt Unit is replaced and sending data to ground control. Main task for #spacewalk complete!
They did this when the ISS was in darkness, to avoid the risk of high-voltage sparks.
According to ground control, the replacement part worked and the station is back to full power.
In the second half of their spacewalk, Peake began installing new cables on one part of the station while Kopra was to install a new vent at another part.
But when Kopra reported water inside his helmet, the spacewalk was cut short.
A commentator on NASA TV stressed that this was not an emergency situation, but was a precautionary measure following a more extreme event in a July 2013 spacewalk, when astronaut Luca Parmitano's helmet filled with water.
During the walk, Peake's wife, Rebecca, tweeted this view from his helmet camera showing a photo of their two sons that was attached to his spacesuit. 😍
@astro_timpeake thank you for taking our boys with you into the vacuum of space 😍🚀🇬🇧👣
UPDATE
After returning to the ISS, Peake tweeted a series of photos, including a spectacular spacewalk selfie.
Today’s exhilarating #spacewalk will be etched in my memory forever – quite an incredible feeling!