Can't wait for them to open source the code once it finally dies. Right now they probably can't do that because of security concerns.
The source code isn't hiding in a repo somewhere for security reasons — it's spread around on various pieces of paper and computers over the last 50 years. There isn't a single source of truth. Adds a whole other level of wizardry to keeping the thing running.
How has nobody at the top ordered a digitization and consolidation of all known code and supporting documentation during that time frame.
Having a ton of people run around the office for a couple months to collate a bunch of documents so you can better pass info on to a new generation of workers when the satellite might not even be usable anymore isn't very efficient. Might as well just pay an extra 50% or whatever to the 5 dudes who know what's going on until the thing is inop. Even if it died today, the mission still would've been a massive success.
Does anyone know whether the Voyagers even do any command authentication?
Probably doesn't matter now as only the dsn has the ability to talk to them, and that happens comparatively rarely.
Even if not, it should be fairly straightforward to compute its position from the initial flightplan. Once it escaped Jupiter its trajectory is just a straight line.
I honestly don't know that we understand gravity well enough to keep this close of track of this small of an object for so long. Plus all the effects of the "negligible" gravities of nearby objects have to add up over time, and we can only include so many bodies in our N-bodies simulation, right?
The problem is simply that you need a huge transmitter with (AIUI) some special and unique modulation hardware. Also there's nothing to be gained from interfering with the Voyagers. Really the only practical thing you could do is shut them down a couple of years before they die anyway. There's just no point.