Astronauts Thomas Marshburn and Kayla Barron were due to scale the outside of the space station today in order to mend a faulty antenna.
The faulty S-band radio communications antenna assembly, now more than 20 years old, was to be replaced with a new spare stowed outside the space station.
However, Nasa issued a debris notification on Monday evening and the mission was called off.
“Due to the lack of opportunity to properly assess the risk it could pose to the astronauts, teams have decided to delay the spacewalk until more information is available,” the agency said.
“The space station schedule and operations are able to easily accommodate the delay of the spacewalk.”
It was not made clear how close debris had come to the ISS, which orbits approximately 402km above the Earth.
Debris is becoming an increasing problem for space operations. The amount of objects, their combined mass and their combined area has been steadily rising since the beginning of...