https://www.businessinsider.com/engineers-turn-to-voyager-de...

> During the first 12 years of the Voyager mission, thousands of engineers worked on the project, Dodd said. "As they retired in the '70s and '80s, there wasn't a big push to have a project document library. People would take their boxes home to their garage," Dodd added. In modern missions, NASA keeps more robust records of documentation.

Nowadays we've learned to make a duplicate.

https://www.jpl.nasa.gov/news/nasa-readies-perseverance-mars...

Back when the Spirit rover got trapped, they used its twin to pre-game possible approaches in similar soil.

https://www.jpl.nasa.gov/news/mars-and-earth-activities-aim-...