Isn’t it fascinating how the Voyager spacecraft keep sparking the public imagination? When Voyager 2 flew past Neptune in 1989, the encounter was almost elegaic. It was as if we were saying goodbye to the doughty mission that had done so much to acquaint us with the outer Solar System, and although there was talk of continuing observations, the public perception was that Voyager was now a part of history. Which it is, of course, but the two spacecraft keep bobbing up in the news, reminding us incessantly about the dimensions of the Solar System, its composition, its relationship to the challenging depths of interstellar space the Voyagers now enter.
In the public eye, Voyager has acquired a certain patina of myth, a fact once noted by NASA historian Roger Launius and followed up by author Stephen Pyne in his book Voyager: Seeking Newer Worlds in the Third Great Age of Discovery:
…the Voyager mission tapped into a heritage of exploration — that was its cultural power. But there was always to the Grand Tour a quality that went beyond normal expeditioning, a sense of the providential or, for the more literary, perhaps of the mythical. The aura would have embarrassed hardheaded engineers intent on ensuring that solders would not shake loose during launch and electronics could survive immersion in Jovian radiation. Yet it was there, a tradition that predates exploration and in fact a heritage that Western exploration itself taps into.
Part of that mythos is the fact that the Voyagers persist, year after year, decade after decade, with perhaps another ten years ahead before they go silent. People who were born the year of the Voyager launches are now in their 34th year, and as of this morning (local time) at 1307 UTC, Voyager 1 has flown 19,228,196,899 kilometers and counting. And just when we’ve begun to absorb the distances and ponder the continuing data return, Voyager does something new to catch our eye, in this case a roll maneuver on March 7 needed to perform scientific observations.
A Star to Guide Us
Something new? Ponder this: Except for a test last month, the last time Voyager performed a roll like the 70-degree counterclockwise rotation (as seen from Earth) it performed this week, it was to snap a rather famous portrait, an image of the planets around the Sun including the ‘pale blue dot’ of Earth. That was back in February of 1990, fully 21 years ago, although to me it seems like yesterday. This time the roll was for a different purpose. Rather than looking back, the vehicle was looking forward, orienting its Low Energy Charged Particle instrument to study the stream of charged particles from the Sun as they near the edge of the Solar System.
The new roll, held in position by spinning gyroscopes for two hours and 33 minutes, tells us that the old spacecraft still has a few moves left. Suzanne Dodd is a Voyager project manager at JPL:
“Even though Voyager 1 has been traveling through the solar system for 33 years, it is still a limber enough gymnast to do acrobatics we haven’t asked it to do in 21 years. It executed the maneuver without a hitch, and we look forward to doing it a few more times to allow the scientists to gather the data they need.”
You may recall that back in June of last year, the same Low Energy Charged Particle instrument began to show that the net outward flow of the solar wind was zero, a reading that has continued ever since. The question now under scrutiny is just how the wind — an outflow of ions from the Sun — turns as it reaches the outer edge of the heliosphere in the area known as the heliosheath. Outside the ‘bubble’ of the heliosphere is the interstellar wind, and the complex interactions between our own star and the interstellar wind are now Voyager’s raison d’etre.
It gives me a kick to realize that when the recent test roll was accomplished on February 2, the spacecraft quickly re-oriented itself by locking onto a guide star with some resonance here, Alpha Centauri. And now that the Low Energy Charged Particle instrument team has acquired what it needs, mission planners are looking to do another series of rolls in coming days as the study of the heliosheath continues. I admit to liking the idea of Alpha Centauri as a guide star for all it conjures up about bright stars in southern skies and ancient voyaging deep into wine-dark seas.
Making the Interstellar Case
Does it also point to future voyaging as we venture outside the range of our own Solar System? Let’s hope so. It’s interesting to see that Stephen Hawking and Buzz Aldrin have joined forces in what they’re calling a Unified Space Vision to “…continue the expansion of the human presence in space and ensure the perpetuation of the species.” Voyager, of course, is a robotic presence, but as we push the boundaries of artificial intelligence with ever more sophisticated probes, we’ll be finding out how the human angle meshes with robotic investigations. I suspect the distinction between living and robotic is going to be less significant as we extend our reach outward.
Human or robot, deep space demands what I might call a rhetoric of interstellar flight, and maybe that’s where Hawking and Aldrin come in, along with The Planetary Society, and Project Icarus, the British Interplanetary Society and Tau Zero. Because Voyager continues to capture the imagination, and that tells me that the innate quality that makes people explore is not a trait we have lost in our time. One of the three ancient arts of discourse, rhetoric is all about how you make the case for something. It’s a way of framing a debate, using language persuasively, and when used right it’s the counterpoise to sophistry. A skilled rhetorician can convince you of the merits of a case, but he or she will do so using logic as a way of getting at underlying truth.
We need to make the interstellar case. It’s the one triggered by every new report from spacecraft that really are going where no one has gone before, and it relies on our understanding that even as we work to solve problems here at home, we must not stop dreaming and planning for a future that pushes our limits hard. Recently we’ve discussed the effects of tightened budgets on NASA missions to the outer system, but the larger picture — the one we need to bring to the public — is that the time-frame for our explorations is less essential than the persistent effort to make them happen. We’ll build a future in space one dogged step at a time, and when asked how long humanity will struggle before reaching the stars, we’ll respond, “As long as it takes.”