I'd be interested in learning more about the flight computers, and in particular the very lowest-level systems used to reset or debug the main systems.
Given the tiny amount of storage, there's presumably no scope for rolling back changes after an error, so are they at risk of bricking the spacecraft every time the flight engineers (and just for once, I think the term "software engineer" is truly justified) make a change?
> Because of the spacecraft’s age and the communication lag time, there’s some risk the patch could overwrite essential code or have other unintended effects on the spacecraft. To reduce those risks, the team has spent months writing, reviewing, and checking the code. As an added safety precaution, Voyager 2 will receive the patch first and serve as a testbed for its twin. Voyager 1 is farther from Earth than any other spacecraft, making its data more valuable.
> The team will upload the patch and do a readout of the AACS memory to make sure it’s in the right place on Friday, Oct. 20. If no immediate issues arise, the team will issue a command on Saturday, Oct. 28, to see if the patch is operating as it should.
> 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.
AIUI, the systems are designed to reset to a known good "standby" state if they don't receive any commands after some time. Of course the recovery routine itself can't be guaranteed, especially when the hardware itself is wonky, but suffice to say the updates aren't completely rawdogging it every time. There's an overview of how it works at https://voyager.jpl.nasa.gov/mission/science/thirty-year-pla...
> Voyager's flange basically works on the same principle, but I knew it had to be designed to last a very long time. Viking's life was short by comparison. Voyager? I planned on an infinite life. Yeah, you're right: the "flange" on Voyager looks like a solid piece of metal attached to the top of the tape reel. Well, actually, not exactly. It's a "shell" made of titanium, within which a flange is mounted through a bearing to the center of the flange assembly. However, after sealing it using electron-beam welding, it was backfilled with a dampening fluid/oil to take the place of the vibration absorbing rubber in Viking. Then, the seal is thoroughly completed using more electron-beam welding. And good news! It will survive a very long time! Like forever.
> The great benefit of handling magnetic tape has wonderful benefits (well, back in its day) - the tape is barely handled in specialized transports like this, but most people didn't really understand how little the tape is touched, even if they may have noticed. Not many did. Once the clear "drive" belt no longer touches the backside of the magnetic tape (look at the photo to see where they separate), it moves freely, toward the tape read/write head, with only the precise distance needed for the tape, as it freely slides through the very narrow slot in the tape head. Well, that's just the introduction to the real problem. Go back to the previous discussions about the tape flanges. That's where the problem was resolved.
The tape in Voyager is closer to a metal strip, so to core memory. The tricky part is in how it is moved with little friction and head still being focused.
I always love the detailed breakdown of how NASA/JPL/ESA keep these ancient machines going at the such an extreme remove. It's always interesting how they shuffle commands around the increasingly geriatric computers to keep them from collapsing and turning into space junk.
We're stuck here, y'all. Better start getting along.
reply