“With a one-way light time of 18.5 hours for the command to reach Voyager, it took 37 hours for mission controllers to learn whether the command worked.”
A planned command sequence on July 21 tilted Voyager 2’s antenna 2 degrees off Earth and cut it off. The fallback was waiting until an automatic reset on Oct. 15. Canberra instead shouted a command 12.3 billion miles and got science data back on Aug. 4. JPL made the mistake and JPL fixed it, which is more than most software vendors manage at zero light-seconds.