An external comms box on the International Space Station has failed, leading NASA to schedule its first unscheduled spacewalk since 2015.
After a software upgrade in March, a multiplexer/demultiplexer (MDM) data relay on the S0 truss failed on Saturday, so command routing is being handled by a backup unit for now.
According to NASA, the box controls radiators, solar arrays, cooling loops and other hardware, but its failure “has had no impact on station activities”.
Station commander Peggy Whitson – one of two members of the crew for Tuesday's spacewalk, with flight engineer Jack Fischer – spent Sunday preparing the replacement unit.
Whitson and Fischer are expected to spend two hours on the spacewalk to swap out the failed mux/demux.
The multiplexer failed at 1:13pm US Central Time on Saturday, and NASA says the cause of the failure is unknown.
As well as replacing MDM-1, Fischer will be installing a pair of wireless antennas on the Destiny Lab.
NASA will be streaming the spacewalk on NASA Television, starting 6:30 am (US Eastern Daylight Time) on Tuesday. ®