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.
It costs money that would better be sent towards other projects, and NASA needs to be as careful as possible with spending their very limited budget.
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.
Given how simple the computer is, I very much doubt it. If anything, it might have a very simple xor encryption or just a passphrase. If anyone were sufficently motivated, it probably would be trivial to snoop on the DSN transmissions and crack any authentication. I'm sure it'd be susceptible to a simple replay attack at any rate
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.
Even if you magically had your own DSN, would anyone but NASA even know exactly where they are with enough precision to communicate with them? In a way, that's now your layer 1 authentication key. The coordinates of where to "point" your DSN.
I'd be very surprised if its exact position in the sky is not public information.
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.
>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?
I was about to say that Voyager likely also suffers from the Pioneer anomaly, which is suspected to be caused by the RTG's thermal radiation pushing the craft off course [1]. But according to wikipedia we can't really tell because the effect of the maneuvering thrusters that keep Voyager aligned is much bigger than the Pioneer anomaly (Voyager 1 has fuel until about 2040).
