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Voyager and Mission Longevity

Sometimes it’s helpful to look back at the original intent of a space mission. Extending missions is all about continuing to do good science, and it’s often a major benefit of missions as successful as Voyager. But consider the Voyager parameters when the two craft launched in 1977. The plan: Study Jupiter and Saturn, as well as their larger moons and Saturn’s rings, with spacecraft that were built to last five years.

That primary mission, of course, was completed and led on to Voyager 2’s flybys of Uranus and Neptune, and Voyager 1’s crossing into the interstellar medium, a 40-year mission still returning data. Voyager 2 will make a similar crossing within the next few years.

I’ve said a lot about Voyager in this space and have even advocated a final thruster burn for each when the two craft reach the end of their energy supplies, in a purely symbolic trajectory change that would bring them closer to nearby stars than they otherwise would travel (see Voyager to a Star).

This goes back to a Carl Sagan notion that Jim Bell also discussed in his book The Interstellar Age (Dutton, 2015). The two stars in question are Gliese 445 (Voyager 1) and Ross 248 (Voyager 2). Here’s a snip from my essay on the matter:

Carl Sagan and the team working on the Voyager Golden Record wondered whether something could be done about the fact that neither Voyager was headed for another Solar System. Is it possible that toward the end of the Voyagers’ active lifetimes (somewhere in the 2020s), we could set up a trajectory change that would eventually lead Voyager as close as possible to one of these stars? Enough hydrazine is available on each craft that, just before we lose radio contact with them forever, we could give them a final, tank-emptying burn. Tens of thousands of years later, the ancient craft, blind, mute but still more or less intact, would drift in the general vicinity of a star whose inhabitants, if any, might find them and wonder.

As I said, purely symbolic, but I think the symbol is powerful. But someday we’ll be sending craft on long-duration missions with the hopes of delivering more than an ancient, silent relic. We’ll want deep journeys coupled with robust data return. Thus a key question for any deep space travel is the lifetime of a spacecraft, and what a heartening example the Voyagers have set by outlasting their original parameters. Can we really build craft that could return data for centuries on missions as far out as the Oort Cloud, or beyond?

Firing Up Voyager

We learn with each new mission, but in terms of Voyager, we’ve just been given another example of how robust even these early spacecraft are. In a move that scientists believe will extend the lifetime of Voyager 1 by two to three years, engineers have fired backup thrusters that have not been used for 37 years. Made by Aerojet Rocketdyne, Voyager’s MR-103 thrusters were highly useful during the Jupiter and Saturn flybys, orienting the craft as they made observations of the planets and their huge number of moons.

The trajectory correction maneuver (TCM) thrusters are located on the back side of the spacecraft, identical to the craft’s attitude control thrusters, but because Voyager 1’s last planetary flyby was at Saturn, there had been no need to use them since November 8, 1980. During the Saturn encounter they were in continuous firing mode rather than the short bursts that the attitude control thrusters normally employ.

On November 28, 2017 engineers fired the four TCM thrusters on Voyager 1 and tested spacecraft orientation changes using 10-millisecond pulses. A wait of 19 hours and 35 minutes followed, reminding us just how far from home (141.3 AU, or 21.1 billion kilometers from Earth as of this morning) Voyager 1 now travels. But the TCM thrusters worked without flaw.

Waking up these thrusters is fascinating in its own right, but it was also a necessary move. The attitude control thrusters on Voyager 1 had been degrading, requiring more firing to achieve the same effect. In any case, Voyager 1 was already using its set of backup attitude thrusters.

But switching to the TCM thrusters to perform spacecraft orientation wasn’t cut and dried. It required unearthing data that hadn’t been examined in decades. Given the amount of time since the original software was written, the Voyager team had to wade into assembler language that is now long outdated. Todd Barber, a propulsion engineer on the mission at JPL, catches a bit of the mood as the news of successful operation finally came in:

“The Voyager team got more excited each time with each milestone in the thruster test. The mood was one of relief, joy and incredulity after witnessing these well-rested thrusters pick up the baton as if no time had passed at all.”

Image: An artist concept depicting one of NASA’s twin Voyager spacecraft. Humanity’s farthest and longest-lived spacecraft are celebrating 40 years in August and September 2017. Credit: NASA/JPL-Caltech.

Now that the TCM thrusters have been tested, the plan is to switch to them in January, although there is a price: Voyager 1 will need to turn on one heater per thruster, itself a use of precious power. When the heaters are no longer an option, the plan will be to switch back to the attitude control thrusters. A similar test will probably take place for Voyager 2.

Can we build spacecraft capable of enduring generations as they tackle increasingly distant missions beyond the Solar System? The evidence from the Voyagers is that the idea is realistic. What a tribute to the original engineering of these craft that they are still in the news.


{ 29 comments… add one }
  • Infinite123Lifer December 4, 2017, 14:21

    The stuff of legends.

  • Alex Tolley December 4, 2017, 14:27

    The Voyager probes used quite primitive electronics compared to our current probes. In particular, as the CPUs become much more powerful, their transistor and connection widths decrease, making them more vulnerable to GCR damage. I expect this trend to continue, with strategies of redundancy and self-healing chips to mitigate some of that radiation damage with long journey times. For AIs on future missions, neuromorphic chips may prove more robust than current architectures, but that is speculative.

    Without some sort of self repair, probe mission times may paradoxically become shorter as the chips become more vulnerable to radiation damage and fail earlier. For interstellar journeys of more than a few decades, e.g. centuries, probes may fail long before they reach their targets. I suspect that even with orientation changes, Breakthrough Starshot must deal with the problem of its chips being rendered inoperative by GCRs rather than by colliding with the ISM.

    I would be interested in hearing from team members about how they intend to deal with that problem (assuming I am correct that GCRs are a problem for their proposed journey times).

    • ole burde December 4, 2017, 16:33

      Silicon based computing is probably not the way to reach long term reliability in space , or even on earth . Many other solutions have been investigated and developed to a certain level , and several of them have important advantages, such as DNA computing , microdots and optical computing ….but the ultimate solution would be to combine several different systems into task-differentiated hiraky : as an example ,microdots when ”printed” on gold might have a thousand year lifetime , and could be the ”safe copy” from which other systems could regenerate damaged code

      • Alex Tolley December 4, 2017, 17:00

        While you can make very robust storage systems, you still need a method to read it back into operating code. If that system isn’t robust, it still fails. It is a bit like carving pictographs on stone. They last 1000s of years, but if the humans who can read it disappear, they become useless.

        Life is perhaps the best example of robust, carbon based computation. If the nematodes and tardigrades survive a voyage to Proxima and can reproduce on arrival, then that would be a start. But they should also be active on te journey too, to prove that some sort of computation can be robust. We know bacteria change quite rapidly on the ISS, so I would be a bit skeptical about those organisms having biological code that is robust to changes. It might need some engineering to make them so.

        • ole burde December 4, 2017, 18:13

          The systems ” to read it back” is exactly the kind of problem where the Breakthrough Initiative could make an important contribution , because nobody else sofar has had a good reason to invest in it …if anybody 50 yeas ago would have told us that bulk information would flow freely and automatcly from optival fibers to cupper to wireles vis satelites and back , we probably would have felt this to be an unnecesary complication ….but today these minor buldingblocks of technology are so cheap and reliable that we almost forget the Magic involved : information flows freely across barriers of a fundamental nature …and so will information Processing , before or later ….but the people who do it first , can channel the solutions toward their ends , in our case long term reliabilty

      • Brett Bellmore December 5, 2017, 22:02

        I rather like integrated, field emission vacuum tubes for long duration radiation resistance. They can be miniaturized to a level similar to transistors, but with much greater resistance to radiation and voltage spikes.

    • Randy Chung, SpaceFab.US December 4, 2017, 23:35

      This solution to the problem of radiation damage to integrated circuits sounds very promising, and not that far off:

    • Jeff Wright December 6, 2017, 17:53

      Something like JIMO needs 1970’s tech on the main bus–with cubesat dispensers.

      A question–wasn’t Oumuamua heading in the general direction of one of the Voyagers? A long shot–I know.

  • Hamilton1 December 4, 2017, 17:45

    There’s an interesting article here about how several of the Pioneer craft were also ‘revived’ after decades of silence. So it’s not just the Voyagers –


    • ljk December 6, 2017, 11:39

      I am glad that Pioneer 10 and 11 are not forgotten, as they are often overshadowed by the more advanced and prolific Voyagers. However, they were true pioneers in being the first to cross through the Main Planetoid Belt, flyby Jupiter and Saturn, and then head out of the Sol system. They cleared the way for their more popular fellow travelers. Those achievements cannot be taken away from them.


  • Brad in Dallas December 4, 2017, 20:33

    The folks at longnow.org have been doing some thinking about engineering things to last millennia. Worth a look.

  • DCM December 5, 2017, 4:16

    Maybe the hypothetical beings who find the Voyager craft will be terrified to learn they aren’t alone. It might upset their whole cosmology and their societies, causing them to invent new and better weapons and militarize.
    Or it could start a kind of cargo cult or flying saucer cult similar to the ones we’ve had.
    Unless they’re so different from us we couldn’t make any sense out of their response.

    • ljk December 6, 2017, 12:00

      You will definitely want to read this short story online here:


      We are going to step out of the door and into the wider Universe, whether it is ready for us or not. And vice versa. I also think our imaginations and fears are quite limited when it comes to what could be out there.

      If you can get ahold of the 1973 book The Cosmic Connection: An Extraterrestrial Perspective by Carl Sagan, there is a similar humorous story about ETI finding and interpreting the Pioneer Plaque. This includes aliens who look just like the pulsar map and view its design as an incredibly offensive gesture by them.

      You may also like this wonderful program on the Pioneer Plaques:


  • NS December 5, 2017, 4:42

    “pictographs on stone…last 1000s of years, but if the humans who can read it disappear, they become useless.”

    Yes, the ultimate limits on mission longevity may prove to be scientific and cultural rather than technological. I’m not against launching potentially very long-lived space probes, but we should not be surprised if our distant descendants see them as interesting relics rather than scientifically useful instruments. The science of 500 years from now may be even more radically different from ours than ours is from that of 500 years ago. It will be extraordinarily lucky if we are able to guess the sort of data scientists will be interested in that far in the future.

    • ljk December 5, 2017, 11:21

      If we wait for the future to do things better then it will likely never happen.

      Take the Apollo manned lunar missions as a case in point. Sure, their computer systems were so primitive they make the Voyager computers look like HAL 9000, but the point is they got humans to the Moon, something we are still waiting to have happen again since 1972 despite all of our technological advancements.

      • NS December 6, 2017, 5:15

        Your example would be more applicable to my reservations if the Apollo astronauts had been told “By the way, during the trip to the Moon you’re going through a time warp, and the Earth you return to will be 500 years in the future. We don’t know anything about what it’ll be like, but for sure your families, friends, and all of us will be dead. There’s a fair chance nobody will remember you or your mission, that there won’t be any recovery ships waiting when you splash down, and that either trips to the Moon are so common they’re nothing special, or else nobody is interested in the Moon at all. Have a good flight.”

  • ljk December 5, 2017, 11:32

    Beethoven in space

    Beethoven’s Symphony No. 9

    By Alexander Rehding

    December 3rd 2017

    Katie Paterson has always wanted to shoot Beethoven to the moon. In Earth-Moon-Earth (2007) the Scottish conceptual artist translated a performance of Beethoven’s Moonlight Sonata into Morse code, sent the radio signals to the moon, and recaptured the reflection.

    What came back of the transmission, having traveled 230,000 miles and back, was refracted on the irregularities moon’s crooked surface, and re-translated into a fragmentary and partial “score” of Morse code, which was then re-sonified and performed on a modern player piano. The absences and gaps in the resulting performance are remnants of the music’s impossible journey to the moon and back.

    Full article here:


    To quote:

    Perhaps the most celebrated instance of Beethoven in outer space is on the Golden Record of the Voyager mission that recently celebrated its 40th anniversary and that has left the solar system, on its way to a galaxy far, far away. The Golden Record is not an artwork in the strict sense, but an interstellar mix tape that Carl Sagan and his team curated for the use of extra-terrestrials in 1977. While the Golden Record had nothing to do with the scientific goals of this space mission, it did manage to capture the collective imagination, by humanizing the idea of outer space. While the disc jockeys that put together the Golden Record made an effort at assembling a collection of different musical traditions from across the world, from Japanese gagaku to Louis Armstrong, and from Mexican mariachi to Indian raga, they deviated slightly from their attempts at inclusiveness and balance by allowing a special place for Bach and Beethoven, who represent Western classical music with multiple compositions.

    The record includes Beethoven’s Fifth Symphony, as one might expect, but also the Cavatina from the String Quartet op. 130, perhaps a less obvious choice. Apparently, this movement was a favorite of Carl Sagan’s—the intense humanity of this piece, underlined in the famous performance indication beklemmt (stifled, inhibited) for the first violin in the contrasting middle section, makes this piece such an intriguing choice. Music critic Alex Ross called it “a wistful farewell” from earth. But second-guessing intentions behind the inclusion of specific pieces matters less than the fact that there is music traveling to the farthest reaches of the universe, as a sign that we humans exist.

    Why Beethoven? One part of the fascination with Beethoven is certainly related to the centrality of his music in our culture. Even the Voyager mission made two slots available for him, in the extremely limited space on the grooves of the Golden Record that was supposed to represent all of earth’s musical cultures.

    For us earthlings, meanwhile, we know Beethoven so well that we can even restore the original sounds under extreme circumstances: we hear the resonances in the gaps of the moon-reflected Moonshine Sonata and the otherworldly slow sublimity of the Ninth, even where the sounds go beyond what our senses are able to perceive.

    • J. Jason Wentworth December 5, 2017, 23:51

      Carl Sagan and Frank Drake as DJs (disc jockeys)…I *love* it! :-)

  • Bill December 5, 2017, 16:53

    I have often thought the fate of the Voyagers is not to travel endlessly through space but to end up in a future museum brought back to Earth by some intrepid adventurer armed with vastly superior spacefaring technology and ancient computer programs of suspect origin revealing their trajectories.

  • Rod L Pyle December 5, 2017, 21:06

    Paul–a great article, thanks so much for writing it. A fun and thought-provoking read.

  • J. Jason Wentworth December 6, 2017, 0:36

    In connection with Voyager 1’s long-dormant TCM thrusters picking up–in a different firing mode, no less–after 37 years as if they’d last fired just two weeks ago, what Randy Chung and Hamilton1 wrote about above (self-healing transistors and the solar-orbiting Pioneer 6, 7, and 8 probes, respectively) is also of great importance for the development of ultra-long-life interstellar spacecraft. Having corresponded with their program personnel recently, I learned that Pioneers 6 – 8 (Pioneer 9 died in 1983) must be commanded “on” in order to transmit, and on all previous occasions they have responded promptly, with no balking or “hiccups,” just like Voyager 1’s TCM thrusters, and:

    The AO-7 (AMSAT-OSCAR 7) amateur radio satellite (see: http://www.amsat.org/two-way-satellites/ao-7/ and http://en.wikipedia.org/wiki/AMSAT-OSCAR_7 ), which was launched in November 1974, went silent in 1981 when its battery failed, then became operational again in 2002, also carries–along with its other beacons and transponders–a 2304.1 MHz beacon which was never activated, due to a change in international radio frequency licensing, and:

    To collect engineering data on the durability of spacecraft and their subsystems after decades of exposure to the space environment, it would be worthwhile to attempt to contact Pioneers 6 – 8 again (the most recent contact with any of these spacecraft–with Pioneer 6–was made in December 2000 [see: http://en.wikipedia.org/wiki/Pioneer_6,_7,_8,_and_9
    ]), and to activate AO-7’s 2304.1 MHz (13-centimeter band) beacon, to see if they will respond, and–if they do–to ascertain the condition of these spacecraft’s equipment. In the case of AO-7, it should be possible to obtain a special, experimental license to activate and monitor the satellite’s never-before-activated 13-cm band beacon, while NASA’s Deep Space Network stations (and/or other radio telescopes) could be utilized to hail Pioneer 6, 7, and/or 8.

  • ljk December 9, 2017, 19:11

    NASA’s famous Voyager probes nearly failed during their rocket launches — here’s what went terribly wrong

    Dave Mosher

    Published 12:13 pm, Wednesday, December 6, 2017


  • ljk December 12, 2017, 15:32

    A celebration of the Voyager Golden Record in its 40th year…


  • ljk December 13, 2017, 12:52

    WeTransfer Announces A Message from Earth: An Online Exhibition with Newly-Commissioned Work, Inspired by The Voyager Golden Record

    To Launch on December 12 on https://amessagefrom.earth

    Includes Exclusive Contributions From Gilles Peterson, Wanda Díaz Merced, Aspen Matis, S U R V I V E, Lawrence Krauss, Fatima Al Qadiri, Oneohtrix Point Never and More…


    LOS ANGELES, Dec. 12, 2017 /PRNewswire/ —

    “We cast this message into the cosmos…a present from a small distant world. We are attempting to survive our time so we may live into yours.” – President Jimmy Carter, on the Voyager Golden Record

    In celebration of the 40th anniversary of The Golden Record project, WeTransfer has partnered with Stink Studios, Gilles Peterson, Oneohtrix Point Never, S U R V I V E, Wanda Diaz Merced and more to present “A Message from Earth.”

    This interactive exhibition of specially-commissioned music, film, art and literature pays tribute to the ambitious, optimistic spirit of the original Golden Record. 40 years ago, a group led by astronomer Carl Sagan set themselves a seemingly impossible challenge – to sum up what it means to be human, and capture these images, sounds, music and greetings on two Golden Records. These were placed aboard NASA’s Voyager I and II, two spacecraft blasted into space to go further than anything man-made had ever gone before. The records were intended as a message from Earth for any extraterrestrial life that might find them.

    The unique online exhibition “A Message from Earth” represents a collage of the contemporary human condition, and features new and exclusive pieces from leading artists, musicians, photographers, authors, and scientists. Their works are commissioned to celebrate themes of hope, determination, and goodwill, are inspired by the original project. The exhibition’s intention is to relay a message of goodwill and encourage further exploration while raising awareness and funding for Astronomers without Borders, the Carl Sagan Institute at Cornell University, and the SETI Institute. WeTransfer is providing $10,000 grants to each institution to initiate public donations, and the project will be commemorated in a $15 limited edition zine with 100% of generated revenues going to the non-profits above.

    “WeTransfer came from the creative community, and as a company we embrace projects like the Voyager Golden Record to inspire us. We’ve collaborated with 40 individuals and organizations from over 20 countries to put this together, and we’re humbled by the people we’ve been able to work with,” says Stephen Canfield, WeTransfer’s VP of Marketing.

    “We’ve had a strong commitment to arts and sciences since 2009, and this felt like a natural next step for us – closely collaborating with amazing people to tell a story that’s inspired so many. The Voyager Golden Record shows what we can do when we come together to create and share something bigger than us, and that feels like a welcome message in 2017. We hope others feel the same, and that we can use this to raise funding for more exploration and selfless acts of cultural diplomacy in the years to come.”

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