NASA, ESA Spacewalkers Install 6.5-Hour ISS Antenna as Tests Show Good Data Link

Q: What is the ultimate backup plan if the space station's final redundant antenna dies before astronauts can install a replacement?

If the ISS lost its last working Ku-band space-to-ground antenna before a replacement could be installed, the station would fall back on its lower-band backup communications — chiefly S-band links — rather than go silent. The reporting around this repair makes clear that Ku-band is the high-speed system used for HD video, large data downlinks and broader crew communications through NASA’s Tracking and Data Relay Satellite System. But NASA also maintains backup paths for “basic telemetry and command traffic.” In practical terms, that means Mission Control could still send commands, receive essential station health data and maintain core voice/contact capability, even if high-bandwidth services were sharply reduced. The tradeoff would be significant. Live television, high-rate science downlink, and other bandwidth-heavy transmissions would be degraded or deferred. Operations would shift into a more constrained communications mode while managers worked to restore Ku-band with a follow-on spacewalk or other contingency repair. So the “ultimate backup plan” is not a hidden third Ku-band dish; it is graceful degradation to the station’s lower-capacity communications architecture, preserving safe command-and-control until hardware redundancy can be rebuilt.

3 articles · Updated · NASA · Aug 25

Anil Menon and Sophie Adenot ended a 6-hour, 30-minute spacewalk at 2:57 p.m. EDT after installing and connecting a spare Space-to-Ground antenna on the ISS.
The antenna is a critical link for high-speed data transmission between NASA Mission Control in Houston and the orbital complex, and initial checkouts showed good power and data flow.
The pair also secured the failed antenna to a spare-parts platform on the station's truss after it had been removed and temporarily stowed during an Aug. 18 spacewalk.
Flight controllers will keep testing the new unit overnight to confirm full functionality; the outing was Menon's third spacewalk, Adenot's second, and the 283rd for station assembly, maintenance and upgrades.