Nasa scrubbed a scheduled spacewalk on the International Space Station (ISS) over threats to astronauts from imminent debris headed towards it. The Tuesday spacewalk was intended to replace a faulty antenna system on the flying laboratory with astronauts Thomas Marshburn and Kayla Barron venturing out of the secure airlock.

The space agency received a debris notification for the International Space Station on Monday evening. However, due to lack of time to assess the threat from the junk, it decided to cancel the spacewalk altogether. “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,” Nasa said in a statement.

Nasa did not say whether the debris was part of the junk created in low-Earth orbit after Russia destroyed one of its satellites earlier this month. The anti-satellite missile test by Moscow led to an international uproar with countries blaming it for polluting the orbit, threatening assets including the Space Station and astronauts.

Following the test, astronauts had to take refuge in the Soyuz and the Dragon capsule in case the debris led to an emergency situation.

WHY WAS THE SPACEWALK REQUIRED?

The spacewalk was required to replace an S-band Antenna Subassembly (SASA) with a spare already available on the station’s truss structure. The antenna recently lost its ability to send signals to Earth via Nasa’s Tracking and Data Relay Satellite System.

The agency has said that although its degradation has had a limited impact on station operations, mission managers decided to install a new antenna to ensure communications redundancy. The spacewalk was scheduled to last over six hours during which Marshburn would have positioned himself at the end of the Canadarm2 robotic arm, working in tandem with Barron.

Meanwhile, astronaut Matthias Maurer of the European Space Agency was tasked with controlling the robotic arm from inside the space station. This would have been the 245th spacewalk in support of the space station assembly. While it was supposed to be the first spacewalk for Barron, Marshburn would have walked out of the safety of the station’s airlock for the fifth time.

The pair arrived for a six-month science mission at the space station on November 11 with the SpaceX Crew-3 mission aboard the Crew Dragon Endurance.