What blows my mind is the organizational knowledge needed after so many years to keep it going. You don't just hand a guy some man pages when he comes onto the project. I'm sure people have aged out, yet they still understand the complexities in the design. That is something we need to understand and prioritize in the systems we build today.
When Voyager failed last year with a CMOS memory error, one of the big problems was that a bunch of low level information was gone or conflicting.
For example, they sometimes had to guess assembler instructions because the code printouts were low quality photocopied pages. Or because there were handwritten comments or comments scratched out with pencil without any clue about why it was done.
One saving grace was the fact that the architecture and the code space was simple enough so that they could reason through the symptoms and actions to take, something that would have been much harder with modern spacecraft.
Startup: "Do you remember when we inserted this quirky module running in AWS? We can use that to implement this next feature. That was a useful decision!"
Voyager: "Do you remember when our parents inserted this quirky module that has since left the solar system? We can use that to turn it off and on again. That was a mission critical decision!"
Not parents for most of us. Grand or great-grandparents. The senior engineers were highly educated and experienced, implying ages 30-50s during development. They are in their 80-100s now.
