≡ Menu

Voyager: Dark Highway Ahead

One rainy night in the mid-1980s I found myself in a small motel in the Cumberlands, having driven most of the day after a meeting and reaching Newport, TN before I decided to land for the night. It’s funny what you remember, but small details of that trip stick with me. I remember the nicking of the wiper blades as I approached Newport, the looming shapes of the mountains in the dark, and most of all the fact that I was thinking about an interstellar mission. I was working on a short story that grew out of the Voyager mission and the experience of those who controlled it.

After a late dinner at a restaurant near the motel, I asked myself what it would be like to be involved in a truly long-term mission. Suppose we develop the technologies to get a probe up to a few percent of the speed of light. If we send out a flyby mission to the nearest stars, we’re talking about a couple of centuries of flight time, or maybe a bit less. It’s inevitable, then, that a mission like this would be handed off from one generation to the next. Clearly the people who worked the stellar encounter would have been born and matured long after the mission left.

My story involved a man who worked on such a mission as the probe closed within a year of its encounter with Epsilon Indi, a man who learned that, although he was only in his 40s, he was dying and wouldn’t see the probe reach its destination. Back in those days the many avenues of exoplanet investigation weren’t yet clear and we had no good data on planets around other stars, so the big question was whether the probe would find planets around the star or not. But the larger issue was the human perspective on time and commitment even in the face of mortality.

I think about things like that every time I read the latest news from Voyager. The most recent information involves a so-called ‘magnetic highway’ and the behavior of charged particles in the heliosheath as Voyager 1 pushes closer to interstellar space. I can check this morning to see that the spacecraft is now 18,462,802,513 kilometers from the Earth, which works out to a one-way light time of just a bit over 17 hours. Voyager 1 was launched on the 5th of September, 1977, but it’s still a live presence that should keep sending back data perhaps for a decade.

There are surely people working around the periphery of the ongoing Voyager missions who weren’t born when they were launched. What would it be like for a civilization like ours to watch a true interstellar mission over the course of lifetimes, a deep space presence that, no matter what else we found ourselves doing would periodically galvanize the attention, reminding all of us that it was still out there, a heart still beating, a mind (human or artificial) still sending back data. There is something grand in that notion that calls up not just physics and astronomy but archaeology, the recovery of history and perspective, of humanity considered over deep time.

But of course when you’re working a mission, you have very practical work to do. Stamatios Krimigis (JHU/APL) is principal investigator of Voyager’s Low-Energy Charged Particle (LECP) instrument. Voyager 1 crossed the so-called ‘termination shock’ in late 2004 and moved into the heliosheath, where the solar wind has slowed and become turbulent. For a time the solar wind dropped to zero and the intensity of the magnetic field began to increase. I sense the practical scientist as well as a bit of the philosopher in Krimigis as he describes all this:

“The solar wind measurements speak to the unique abilities of the LECP detector, designed at APL nearly four decades ago. Where a device with no moving parts would have been safer – lessening the chance a part would break in space – our team took the risk to include a stepper motor that rotates the instrument 45 degrees every 192 seconds, allowing it to gather data in all directions and pick up something as dynamic as the solar wind. A device designed to work for 500,000 ‘steps’ and four years has been working for 35 years and well past 6 million steps.”

A four year design still functioning after 35 is a tribute to the engineering that conceived it and a reminder of the timescales that missions into much deeper space will one day have to reckon with. As to Voyager, has it entered a new region of space? This JHU/APL news release gives useful background: The LECP instrument has seen sudden increases in cosmic rays and decreases in low-energy particles, a varying scenario that has yet to settle down. Krimigis and team are saying that Voyager may be in a new region but not yet in true interstellar space.

Image: This artist’s concept shows plasma flows around NASA’s Voyager 1 spacecraft as it gets close to entering interstellar space. Voyager 1’s Low-Energy Charged Particle instrument detects the speed of the wind of plasma, or hot ionized gas, streaming off the sun. It detected the slowing of this wind – also known as the solar wind – to zero outward velocity in a region called the stagnation region. Scientists had expected that the solar wind would turn the corner as it felt the pressure of the interstellar magnetic field and the interstellar wind flow. But that did not happen, so scientists don’t know what to expect once Voyager actually crosses the heliopause. Credit: NASA/JPL-Caltech/The Johns Hopkins University Applied Physics Laboratory.

The term ‘magnetic highway’ comes up because in this region low-energy particles from inside the heliosphere are flowing out while higher-energy particles are flowing in — the Sun’s magnetic field lines are connected to interstellar magnetic field lines. While charged particles bounced in all directions before Voyager 1 entered this region, as if firmly contained by the surrounding heliosphere, they’re now much more directional. Krimigis again:

“If we were judging by the charged-particle data alone, I would have thought we were outside the heliosphere. In fact, our instrument has seen the low-energy particles taking the exit ramp toward interstellar space. But we need to look at what all the instruments are telling us and only time will tell whether our interpretations about this frontier are correct. One thing is certain ­– none of the theoretical models predicted any of Voyager’s observations over the past 10 years, so there is no guidance on what to expect.”

I suppose it was the ‘magnetic highway’ metaphor that brought back my night drive through the Cumberlands and all the musing about interstellar missions at a time when Voyager 2 had not yet reached Neptune (and Voyager 2, by the way, shows no signs of reaching the magnetic highway at a distance of about 15 billion kilometers from Earth). Voyager project scientist Ed Stone (Caltech), as venerable a figure as they come in the Voyager pantheon, thinks true interstellar space is a few months to a couple of years away for the farthest Voyager.

We’ll lose something priceless when the Voyagers finally go silent, but New Horizons is still robust and that gives me hope. I think we need a continuing voice from the deep dark to remind us that our nature is to explore even if human lifetimes fade to insignificance against the starry backdrop that bore us. Daily work is the thing, and to work for what Tennyson called ‘the long result’ is the best work there is, whether we’re there to see the end of the mission or not.


Comments on this entry are closed.

  • Leon J Williams December 5, 2012, 10:43

    Nice post.

    Completely agree, we must continue to work and develop these important projects even if they span beyond one lifetime.

  • NS December 5, 2012, 22:17

    A number of human institutions as well as artifacts (cathedrals, bridges) have existed and been in use for centuries. So we have some experience of this.

    I wonder though if science does not change so rapidly that any information a long-term space probe might collect two centuries after launch would be of interest to scientists of that time. I don’t know of any comparable situation (I welcome info) where a scientific device built 200 years ago and not modified since is still useful. And there’s the often-mentioned point of a newer, faster probe being able to reach the same destination ahead of the older one. It seems to me that problems like that are more likely to be an issue than the institutional ones.

  • Thomas Mazanec December 6, 2012, 8:26

    I understand that, in the Middle Ages, a young man would be one of those starting the building of a cathedral. It would be half completed when he died of old age, and his grandson would start working on it. That grandson would see the cathedral completed as an old man himself.

  • ljk December 6, 2012, 10:25

    NS said on December 5, 2012 at 22:17:

    “I wonder though if science does not change so rapidly that any information a long-term space probe might collect two centuries after launch would be of interest to scientists of that time. I don’t know of any comparable situation (I welcome info) where a scientific device built 200 years ago and not modified since is still useful. And there’s the often-mentioned point of a newer, faster probe being able to reach the same destination ahead of the older one. It seems to me that problems like that are more likely to be an issue than the institutional ones.”

    LJK replies:

    This attitude of “Let’s wait because things will get better” has one fatal flaw: There is no guarantee that future generations will oblige us with collecting the information and improving on the technology. Especially if our children do not have anything to inspire them with to do these very things you hope for.

    When the first modern era computers came about in the 1940s, some might have said to wait because some day someone will build a computing machine that is much more powerful and much less bulky. But that never would have happened without all the work in-between and in the meantime the current generations would have gone without computers at all.

    Same with Apollo. Sure we could have built more sophisticated spacecraft to do the job down the road, but they did it in the 1960s and brought back hundreds of pounds of lunar surface samples and other vital data which scientists are still using to this day. Note that the government stopped the program in 1972 and we have yet to go back since, despite the fact that we have been technology. Doesn’t do any good if it doesn’t get used.

    You really think the Voyagers’ data collection from regions of space never explored before are a waste of time and money? Maybe something better and faster will come along, but we have the information now that will guide those future probes through those regions of the galaxy.

    And in case you did not notice, there are NO solid plans for such deep space probes other than some white papers. They may not materialize for many more decades and if things get worse economically and culturally, you and your descendants may have a very long wait.

    So no, I am not waiting for warp drive when we can at least start with an Orion or its equivalent. We will learn a lot along the way to reach the stars.

  • lurscher December 6, 2012, 12:37

    there is an ineffable melancholy in the pursuit of interstellar travel and knowledge. We all know, that almost for sure, we will never see with our own eyes none of those worlds, we will read none of the stories of any of those thousands of civilisations that are surely out there, looking at us without seeing us, just as we do. There is nothing more tragic than all that beauty out there going to waste. And i say that it goes to waste because anything beautiful that is not shared is to be lost forever. If an asteroid would tomorrow wipe the human civilization, all our beauty and ugliness will be lost, and it would help nor enlighten no one else. If you don’t feel a deep despair upon this realisation, you cannot care for the epic and enormous challenge that space exploration represents to us, transient wet bags of meat that call themselves ‘humans’

  • ljk December 6, 2012, 16:26

    Lurscher, the true waste is if we never tried these things, whether the results come today or a century from now. Or if we spent our time focused on worrying about events that could bring everything down.

    While I too would like to see in my lifetime a starprobe return results from Alpha Centauri, or the discovery of alien life, or even a permanent space settlement for crying out loud, I will be happy if I know that these goals are at least truly underway for our descendants. We really need to start thinking cosmically and in terms of truly deep time.

    As for a planetoid or comet strike, first the important thing is that we are aware of such a danger. The dinosaurs and every other life form on Earth before us had no clue, so far as we know. We do have the means to reduce the possibility of such a nightmare scenario. What are you and others going to do to make sure we are safer in this regard?

  • NS December 6, 2012, 16:58

    LJK, read what I wrote. I didn’t say “wait until things get better”. I said build things now that address problems we have now. The people who built computers in the 1940s were doing research that was of interest in the 1940s. They didn’t intend them for use by people in the 2140s. In 1969 we could go to the moon and back in a week, and it was perfectly reasonable to do so. But nobody in 2169 is going to fly to the moon with 1969 technology. We should launch space probes in 2012 to answer scientific questions that are of interest in 2012 (and for the foreseeable future). But we should also recognize that it’s unlikely that data returned in 2212 by a probe launched in 2012 will be of much interest to scientists of that time. My argument is this is a larger obstacle to missions of that length than the institutional ones mentioned in the post.

  • Bounty December 6, 2012, 19:54

    NS, why not? These comments follow an article about a probe launched before I was born that’s giving us data that we could not predict. The moral of the story is, we should launch probes in 2012 designed to possibly still answer questions of interest in 2212.

    Lurscher, if it’s any consolation, in our lifetimes we may get the redundancy of solar colonies and asteroid detection networks. We may have telescopes that let us resolve other systems with such detail, that we might as well be on a flyby mission. We may be able to aim these telescopes at many systems. We may have warp drives or cryostatis. We just need to get our s*** together and start building, start lobbying and organizing. The time to act is now.

  • Brasidas December 6, 2012, 21:55

    I do find it encouraging that NASA has kept Voyager functioning (at least partially) for over 30 years, even with 1970’s technology. This shows that probes can funtion in space over a lifespan of decades, which is what would be needed to send a telescope to the where the sun’s gravitational lensing could be useful, and within an order of magnitude or two of what would be needed to send a probes to Alpha Centauri.

  • NS December 7, 2012, 12:45

    Bounty, if a probe lasts 200 years and turns out to be useful the whole time, fine. My contention is that a 200-year mission that does not return most of its data until the end of that time runs into the problem that science itself may have changed drastically by then. A probe like that would be more like a time capsule than a scientific instrument.

  • Eniac December 8, 2012, 11:56

    One of my favorite ideas is the use of deep space probes for long baseline radio interferometry. You could have probes that are really just large radar dishes, alternately pointing to a target to acquire data and back to Earth to send it. Or, better, if there are enough probes, an optical probe-to-probe network could relay the data and the dish could be on target all the time. On Earth, the data is combined, providing spectacular angular resolution due to the long baseline. Such an “instrument” would get more and more capable and accurate with time, as more probes are launched and the baseline grows ever larger. Plotting a course towards a nearby star would be icing on the cake. Practically free, a gift to future generations of researchers.

  • spaceman December 9, 2012, 2:14

    Encouraging how a 4 year design is still operating successfully three and half decades later. This bodes well as far as creating and maintaining instrumentation across the timescales involved in interstellar travel. The Mars rovers, Spirit and Opportunity, would be another example of our space technology persisting far longer than our original expectations for its performance. In fact, I would go as far as to say that the successful function of our first interstellar probe, perhaps taking a few centuries to reach nearby planetary systems, will be less of a concern than the successful function, or even survival, of our civilization over the same time period.

    Paul, I enjoyed the imagery invoked in this post and the story you mentioned sounds like it would make for a good read. Is there a way we can access it?

  • Paul Gilster December 9, 2012, 15:45

    spaceman writes:

    Paul, I enjoyed the imagery invoked in this post and the story you mentioned sounds like it would make for a good read. Is there a way we can access it?

    The story, titled “Merchant Dying,” was published in Aboriginal Science Fiction in the July/August 1987 issue. It was reprinted in Aboriginal‘s May, 1988 annual anthology. Very kind of you to ask! Unfortunately, it’s not online but maybe I can remedy that.

  • NS December 9, 2012, 17:24

    History is our only guide as to whether it makes sense to design a space probe for timescales of 200+ years. I restate the question from my first post on this thread: are there any scientific devices designed circa 1812 which (if still functioning) would provide useful data to today’s scientists? If yes then I will happily concede that for us to design such a probe would be worthwhile. But given how much science has changed in the last 200 years, and how much more it is likely to change in the next 200, I continue to question whether it’s possible to make a reasonable guess about what scientists of that time will have use for.

  • ljk December 10, 2012, 11:09


    The Physics arXiv Blog

    December 7, 2012

    Voyager 1 Hits Rumble Strips At the Edge of the Solar System

    NASA’s oldest interstellar spacecraft is suddenly measuring changes more dramatic than any it has seen during its 35 year journey.

    Something strange is happening to the Voyager 1 spacecraft.

    After 35 years of travel, NASA’s oldest interstellar spacecraft is now some 20 billion kilometres from the Sun. It’s easy to imagine that conditions in this isolated region of space would be quiet and calm but on 25 August, the spacecraft’s instruments suddenly went haywire, recording changes unlike anything it has seen throughout its long journey.

    Today, Bill Webber at New Mexico State University in Las Cruces and a few pals detail the dramatic changes Voyager has experienced and suggest various explanations for the phenomenon.

    Voyager 1 is currently investigating the outer reaches of the Sun’s influence, the region where the solar magnetic field ploughs into the galactic field as the Sun moves through the Milky Way. This creates a magnetic bow wave that traps charged particles in various ways.

    One of the important tasks for Voyager is to measure these particles, which fall into two types. The first are protons, electrons and nuclei accelerated to high energies inside our galaxy by processes such as supernovas. These are called galactic cosmic rays.

    The second are similar charged particles accelerated to lower energies by a different mechanism–the Sun’s magnetic field. These are called anomalous cosmic rays and, because they are accelerated by a different mechanism, their intensity changes relative to the galactic cosmic rays.

    Indeed it was the intensity of anomalous cosmic rays that changed so dramatically on 25 August. Webber and pals say the intensity of anomalous cosmic rays dropped some 500 times in just a few days. In that time, Voyager 1 travelled only 14 million kilometres.

    That’s like falling off a cliff. “The magnitude of this intensity change for anomalous cosmic rays has never previously been observed in the 35 year Voyager 1 mission except for the Jupiter encounter,” say Webber and co.

    Clearly, the spacecraft has moved into a region of space that is more or less free of anomalous cosmic rays.

    That’s hugely important because it has revealed something entirely new: the low energy galactic cosmic rays that are otherwise drowned by the numbers of anomalous cosmic rays. Webber and co describe this discovery as “one of the holy grails of galactic cosmic rays studies”.

    Another interesting feature of this event is that Voyager 1 experienced temporary drops in the intensity of anomalous cosmic ray particles on 28 July and 14 August.

    Webber and co say there could be two different explanations for this. The first is that the boundary that Voyager crossed is uneven and moving at roughly the same speed as the spacecraft. So the probe has moved back and forth across it several times.

    The second possibility is that the boundary has a ribbon-like structure, creating a kind of magnetic rumble strip for the spacecraft to pass over.

    Either way, Voyager is in a new region of space that will give space scientists new insights into the nature of interstellar space and the galactic medium.

    Long may the mission continue.

    Ref: http://arxiv.org/abs/1212.0883 :

    At Voyager 1 Starting On About August 25, 2012 At A Distance of 121.7 AU From the Sun, A Sudden Sustained Disappearance of Anomalous Cosmic Rays and an Unusually Large Sudden Sustained Increase of Galactic Cosmic Ray H and He Nuclei And Electrons Occurred

    [This title is almost worthy of belonging among those titles given to science papers and books in the days of yore which were also about ten miles long and practically explained and contained the entire work by itself.]

  • Eniac December 10, 2012, 22:50


    are there any scientific devices designed circa 1812 which (if still functioning) would provide useful data to today’s scientists?

    I would offer the scale, the clock, the compass, and the sextant as devices that even in their original form would still be pretty useful today, if their more powerful modern descendents were unavailable.

  • KevinC December 12, 2012, 3:30


    Location, location, location. If we had some kind of Steampunk interstellar probe from 1812 in another star system, and it was able to send us data, it would be useful. In the same way, Voyager is useful to us despite its age because of where it is. Apart from some kind of faster-than-light interstellar drive (which is basically magic as far as we can tell), the only way to get a probe to another star system is going to be something like a rocket (VASIMR, etc.) or a solar sail or magnetic sail. Which means, any probe we send is going to be decades or centuries old when it gets to its destination, no matter what technology the future might offer (again, barring FTL).

    And, even if we do get some kind of faster STL interstellar drive in The Future, we could send probes to other star systems or even to the same one without necessarily making the first probe useless. We have sent out more than one probe to explore our solar system, and could easily send dozens more without making any of them redundant. Realistically, a probe we launched now would only be useless in 2212 if we were able to gallop past it in the Starship Enterprise, which is (unfortunately) not bloody likely.

  • Tiens van Greuning March 6, 2013, 19:44

    Aye, one has to wonder whether, 621 years later, Europeans think it was a useful endeavor to send Columbus searching for a westward sea-passage to India, and with 1490’s vintage sailboat technology at that…