Voyager 2’s Plasma Spectrometer Turned Off In Power-Saving Measure

The Voyager 2 spacecraft’s energy budget keeps dropping by about 4 Watt/year, as the plutonium in its nuclear power source is steadily dropping as the isotope decays. With 4 Watt of power less to use by its systems per year, the decision was made to disable the plasma spectrometer (PLS) instrument. As also noted by the NASA Voyager 2 team on Twitter, this doesn’t leave the spacecraft completely blind to plasma in the interstellar medium as the plasma wave subsystem (PWS) is still active. The PLS was instrumental in determining in 2018 that Voyager 2 had in fact left the heliosphere and entered interstellar space. The PLS on Voyager 1 had already broken down in 1980 and was turned off in 2007.

After saving the Voyager 1 spacecraft the past months from a dud memory chip and switching between increasingly clogged up thrusters, it was now Voyager 2’s turn for a reminder of the relentless march of time and the encroaching end of the Voyager missions. Currently Voyager 2 still has four active instruments, but by the time the power runs out, they’ll both be limping along with a single instrument, probably somewhere in the 2030s if their incredible luck holds.

This incredible feat was enabled both by the hard work and brilliance of the generations of teams behind the two spacecraft, who keep coming up with new tricks to save power, and the simplicity of the radioisotope generators (RTGs) which keep both Voyagers powered and warm even in the depths of interstellar space.

24 thoughts on “Voyager 2’s Plasma Spectrometer Turned Off In Power-Saving Measure

      1. There will be a date when they shut the last instrument off to save power, and then it’s just engineering data. You’d like to say “just keep that!” but it takes a lot of effort to receive and command via the DSN. You don’t do that just for fun.

  1. They won’t shut it down….it will just run out of power and fail. The amazing Voyager team will keep them working as long as they can. See movie about Voyager team …inspiring dedicated people

    1. It’s not an easy question as to how the program will end: the “bare minimum” amount is ~200 W (the VIM challenges paper says 200/198 for V1/V2, but they are sneaky) – by model, that’ll hit in ~2030. But the thruster fuel is marginal over that same timescale too, and it’s unlikely that NASA will keep the program running once the last instrument turns off.

      It’s kindof an open secret that they’re aiming for the ~2027-timescale for the 50-year anniversary. Once that hits, it’s likely that they’ll just end the program.

      1. A diverse group is more likely to have been chosen based on merit. No one group has a monopoly on merit and if you just happen to hire mostly people who just happen to be “a lot like me”, you’re probably missing out on better people. I worked for 20 years for an initially small company that was founded by former NASA contractors in the 1980s (contemporary with the hiring of many of the folks in the “It’s Quieter in the Twilight” movie) who brought on a diverse workforce, many also with NASA experience, that powered the rapid growth of the company. In later years, as the NASA veterans retired or moved on, the original civilian/commercial side of the company on which I worked got increasingly less diverse. The defense contracting side of the company continued on hiring diverse employees and became the predominant part of the company. There are obviously factors other than diversity that affect a company, but the fact is that the original founders didn’t limit themselves in who they hired and the result was a thriving company, significant in its particular market, and with 200-300 employees.

        1. That used to be more true than it now is, because originally the “non-diverse” groups were putting visible signs of difference as more important than merit, and the ones that weren’t doing that got more of the meritorious people who didn’t fit in. But now, we also sometimes deliberately put visible signs of difference above merit in the other direction. And when I say visible signs, I mean that we only care about diversity when we can tie it to, for example, race, ethnicity, or sex. We don’t seem to think it’s worth caring about having a diverse mix of introverts and extroverts, or perfectionists and big-picture people. We don’t seem to think it’s diverse to have both someone from NYC and someone from Montana unless one of them looks different from the other visually. And it’s not just if they look visually different from a generic caucasian guy; we also don’t seem to care if people from India who climb the ladder are from upper castes and discriminate against lower castes in hiring and promotion decisions. Do people who otherwise champion diversity just think all Indians are interchangeable or some nonsense?

          And another example: It’s not a good thing that the overwheming majority of people going into various computer fields are men; it’s unarguably certain they aren’t the only ones who had the potential to learn. But it’s already that way in schools, not even college but also K12. So if you see a random large company whose IT workforce is composed of say, 60% women, you might be tempted to think “hey, that’s great!”. But if there’s still say nine or ten times as many men graduating with appropriate degrees, and a fairly equal number of people at that company being hired of each sex, then there’s only a few ways that company could be merit based. Maybe women are just ten times more likely to be good with computers, but I doubt it. Maybe there’s really so many other companies that are excluding non-men that this one company that doesn’t was able to filter through a similar number of men as non-men and pick the best of both. Maybe there’s something about this company that makes fewer men apply, although it’s hard to think of something that would account for the discrepancy without being very exclusionary. When I was a kid, the teachers in just about every computer class were women, and in the advanced classes that did programming, I even had one that heavily encouraged girls to join her classes, to try out for the interscholastic academic competitions, to attend girls-only extracurricular coding classes, or to get extra help from her if they were considering dropping the classes. Their numbers still dropped like a stone after the last mandatory computer class, unfortunately. She at least was fair enough in grading, and as a result didn’t interfere when the top of the class and the members of the team happened to be male anyway. But it highlights that the problem comes from so early on that by the time anyone’s hiring workers, 50/50 is incredibly unlikely to occur by chance.

    1. Just watched the documentary. Its a bit light on the technical details (which is expected) but still very cool nonetheless.

      Makes me want to design and build something that works for decades without human intervention and just…does what its supposed to.

      1. What if you build a town where every houses roof is electromagnetically reflective and formed in such a way that together they form a patchwork parabolic dish – and the radio tower in the town center doubles as a Receiver…

        I mean it would be difficult to get an Arecibo-like moveable antenna but maybe a phased array?

        When the town is not in a valley I guess it wouldn’t work without a phased array anyway (if it can work at all)…
        Maybe one phased array per roof-set (roofs that are aligned together)?

        One could even hide it all cold-war-style – the receiver in a GIANT church tower and the rest is easy. ;-)

    1. While we’re in the pedant’s corner, ” 4 Watt/year ” and ” 4 Watt of power ” should be ” 4 watts/year ” and ” 4 watts of power “. (plural and not capitalized).

      (I’m waiting to see the singular of “hertz” used in these pages.)

      1. Psst: The definition of “hertz” is “one hert per second”
        Pass it on…
        (I want to see this pop up in a forum in 3 months, followed by a wikipedia entry, with references and everything)

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