NASA, ESA Astronauts Set 6.5-Hour ISS Spacewalk to Install High-Speed Antenna

Q: What unexpected challenges forced the astronauts to abandon this critical antenna installation during their previous spacewalk?

They had to abandon the installation because the earlier spacewalk was slowed by stubborn hardware and ran out of time. During the Aug. 18 EVA, Anil Menon and Sophie Adenot successfully removed the failed space-to-ground antenna, but several unexpected problems made the job take much longer than planned. The astronauts struggled to free tight power and data connectors, had difficulty installing locking pins in the antenna’s gimbal assembly, and needed extra effort to unbolt the unit from its boom, including heavy use of a ratchet wrench. Those delays consumed the time needed for the second half of the task: moving the old antenna to permanent storage, retrieving the spare, and installing it. Mission Control ultimately directed the pair to secure the failed antenna near its boom and defer the replacement to a follow-up spacewalk. NASA noted that the station still had one working antenna, so communications were maintained, but restoring the second unit remained important for redundancy and long-term reliability.

Q: With only one functional antenna left, what catastrophic communication risks does the ISS face if this high-stakes spacewalk fails?

If the spacewalk failed, the ISS would not immediately “go dark,” but it would be left with a dangerous single point of failure in one of its most important communications systems. NASA’s own planning notes say one antenna can support normal operations, but two are needed for redundancy and long-term reliability. The antenna being replaced is part of the station’s high-speed space-to-ground link, used for video, high-rate telemetry and routine communications with Mission Control through NASA’s relay satellite network. With only one working unit, any failure of that remaining antenna would strip the station of its primary high-bandwidth connection. That would not mean total loss of contact. Backup links can still carry basic voice, command traffic and lower-rate telemetry. But the risks would rise sharply: degraded real-time monitoring of station systems, reduced ability to send science data, loss of live video and a weaker communications margin during anomalies, dockings or emergencies. The real catastrophe is not instant isolation, but exposure. A second antenna failure before a replacement is installed could leave controllers and crew relying on slower, more limited backup channels at the exact moment they might need robust communications most. For a permanently crewed spacecraft, that loss of redundancy is itself a serious operational hazard, which is why NASA treats the repair as high priority even though the station can still function on one antenna.

3 articles · Updated · NASA · Aug 25

Tuesday’s EVA is scheduled to begin at 8:35 a.m. EDT, with NASA’s Anil Menon and ESA’s Sophie Adenot heading outside the ISS to finish installing a high-speed space-to-ground antenna.
Monday’s final preparations covered tool setup, spacesuit leak checks and procedure reviews in the Quest airlock after an end-of-shift readiness conference with mission controllers.
Jack Hathaway will operate Canadarm2 from inside the station with Menon attached to reach the Z1 truss worksite, while Adenot stays tethered there to complete connections needed to activate high-speed transmissions.
Elsewhere on Expedition 75, Roscosmos crewmates studied how microgravity affects breathing, activated Earth-observation gear over Asia-Pacific and Africa, and packed the Progress 94 cargo ship for its September departure.