Two US astronauts were set on Tuesday to venture out of the International Space Station (ISS) for a spacewalk to replace a failed antenna, facing what Nasa officials say is a slightly elevated risk from the debris of a Russian anti-satellite missile test.
Nasa TV planned to provide live coverage of the six-and-a-half-hour spacewalk, scheduled to begin at 7.10 ET (12.10 GMT) as astronauts Thomas Marshburn and Kayla Brown exit an airlock.
Their objective is to remove a faulty S-band radio communications antenna assembly, now more than 20 years old, and replace it with a new one stowed outside the space station.
The malfunctioning antenna recently lost its ability to send signals to Earth. Though other antennae on the space station can perform the same function, mission managers decided to install the replacement to ensure a back-up.
Marshburn will work with Barron while positioned at the end of a robotic arm operated from inside the station by the German astronaut Matthias Maurer of the European Space Agency, with help from Nasa crewmate Raja Chari.
The four arrived at the space station on 11 November in a SpaceX Crew Dragon capsule launched from the Kennedy Space Centre in Cape Canaveral, Florida, joining two Russian cosmonauts and a Nasa astronaut already on board.
Four days later, an anti-satellite missile test conducted without warning by Russia generated a debris field in low-Earth orbit, and all seven crew members took shelter in their docked spaceships to allow for a quick getaway until the immediate danger passed, according to Nasa.
The cloud of debris has dispersed since then, according to Dana Weigel, Nasa deputy manager for the International Space Station. But Nasa calculates that remaining fragments continue to pose a “slightly elevated” background risk to the space station as a whole, and a 7% higher risk of spacewalkers’ suits being punctured, compared with before Russia’s missile test, Weigel told reporters on Monday.
He said Nasa had yet to fully quantify additional hazards posed by more than 1,700 larger fragments it is tracking around the station’s orbit, but the 7% higher risk to spacewalkers fell “well within” fluctuations previously seen in “the natural environment”.
Still, mission managers cancelled several smaller maintenance tasks under consideration for Tuesday’s spacewalk, Weigel added.
The exercise marked the 245th spacewalk in support of assembly, maintenance and upgrades of the space station, which this month surpassed 21 years of continuous human presence, Nasa said.