Image copyright AFP
There will be no spacewalk by the astronauts currently working in the International Space Station on Friday.
The planned task had been delayed by five days due to concern about potential space debris near the International Space Station (ISS).
Astronauts Ricky Arnold and Nicole Mann had been scheduled to remove an ammonia tank from the station’s Unity module.
An alert has now been issued at launch, and crews will monitor for debris and work around it, NASA said.
The alert came from an in-flight test of a new orbiter manoeuvring system.
At 1025 GMT on Friday (1725 GMT on Saturday), the alert cleared and the spacewalk went ahead as planned.
Image copyright NASA Image caption Ricky Arnold and Nicole Mann fixed spacesuits on and left from the Russian Zvezda service module
The astronauts used the Russian Zvezda service module’s thrusters to steer themselves out of their orbital home.
They were inspecting the wiring on the ammonia tank, which has been on the ISS since 2002.
They have since plugged and unpluged its four storage tanks and connected it to its third.
The work is seen as key to the long-term safe use of the space station, and many of the long-term tasks on the US side of the ISS are due to rely on its ability to operate effectively.
Image copyright NASA Image caption The spacewalkers also removed an ammonia tank from the space station’s Unity module
The next spacewalk, on Tuesday 5 February, will involve the spacewalkers to make a power connection to a new laboratory due to be installed at the end of March.
The two-man US mission and a Russian mission to Russia’s space station, the Zvezda, will complete the latest round of upgrades in the station’s existence.