If you visit NASA's Missions Finder page and scroll down, you'll see that Voyager is one of only two entries listed under the letter v. That's 119 missions deep in the space agency's use of the alphabet, and more than a generation away from its launch in 1977.
Actually, more than a generation away from both Voyager launches. You have be of a certain age or a farily serious student of space exploration history to recall there were two unmanned Voyager spacecraft. Voyager 2 launched first, in August 1977, taking advantage of planetary alignments to study Uranus and Neptune. Voyager 1 followed in September, arriving at Jupiter and Saturn ahead of its twin. The discoveries made by both crafts greatly expanded our knowledge of these four outer planets and their moons.
Artist's conception of Voyager 2 passing Jupiter, by ElChristou, 2007. Source: CelestialMatters.org
From where I sit, one of the best brief descriptions of their journeys appears in David Grinspoon's Lonely Planets: The Natural Philosophy of Alien Life, hands-down the most entertaining and thought-provoking book on the subject of life beyond Earth written to date. Here's his take:
"During the 1970s and 1980s our eyes were opened to the rest of the solar system by the epic travels of the Voyagers. Launched in 1977, the year after the Viking landings, the two Voyagers flew by Jupiter in 1979 and Saturn in 1980. One craft, the indomitable Voyager 2, made it to Uranus in 1986 and Neptune in 1989. These missions took decades of hard work and intense planning, but the excitement was distilled into brief, manic 'encounters' lasting only several days each, as one of the Voyagers would race past one of these giant planets, feverishly snapping pictures of its cloudy surface and its entourage of moons. Then, having safely radioed the bounty home, the spacecraft would quickly recede into the lonely depths of interplanetary space, heading for the next new world. During each encounter, multiple worlds were transformed instantly from obscure telescopic subjects into concrete, detailed places. The stunning pictures from these bursts of revelation will be treasured by humankind forever."
Grinspoon writes so well about it because he was directly involved:
"For planetary scientists the Voyager encounters were peak, formative experiences, and the trajectories of those two spacecraft through the outer reaches of our solar system became entwined with the trajectories of our lives. When Voyager 2 reached Jupiter, I was a nineteen-year-old undergraduate assisting the team of scientists who retrieved and analyzed the photos beaming back from deep space. At the Uranus enounter I was participating as a twenty-six-year-old graduate student, and at Neptune I was a postdoc pushing thirty."
Good stuff. But now, another thirty-plus years later, relatively few people besides planetary scientists remember what the Voyager craft accomplished, despite some brief media coverage in 2007 marking the 30th anniversary of the launches. Perhaps fewer still know of these additionally remarkable and inspiring aspects of their story: each craft is, of course, still traveling through space and communicating daily with scientists on Earth, and each carries an identical gold-plated record designed to inform any intelligent beings in our galaxy that might discover them by chance one day more about planet Earth via recorded sounds and images.
These days Voyagers 1 and 2 are traveling through the heliosphere, a kind of bubble in space where the Sun's solar wind meets the winds of other stars. As of May of this year, Voyager 1 was about 10.2 billion miles from Earth, Voyager 2 about 8.2 billion. (But for both, the total distance traveled since launch was then nearly 13 billions miles.) It takes signals traveling at the speed of light -- 186,000 miles per second -- more than 15 hours to reach either craft, and vice versa. Only NASA/JPL's Deep Space Network (DSN) antennas are capable of communicating with the probes now.
Given their distinguished history it's not surprising that Voyager discoveries are still being made. Now called the Voyager Interstellar Mission, five instruments on board each craft are today investigating a variety of magnetic field, cosmic ray, and plasma phenomena. Last year data from Voyager 2 confirmed the heliosphere has a "squashed" shape; it's pushed inward closer to the Sun due to an interstellar magnetic field. Knowing this improves our understanding of how solar and interstellar space interact.
And the gold records?
The Voyager "Golden Record" and its cover. Credit: NASA/JPL
The identical discs deserve at least one post of their own (next stop) but for now, I like thinking about them attached to the side of each craft in their mirrored jackets, hurtling along at somewhere close to 10 miles per second on their respective trajectories toward the interstellar medium. How they were proposed, created, and eventually permitted to travel on the probes (it almost didn't happen) is to me just as interesting as the content embedded in the discs themselves.
Space exploration is an expensive, tricky business. And always, a highly complex activity that requires a unique combination of circumstances before any project literally gets off the ground. Harris Schurmeier, Voyager Project Manager from 1970 to 1976, describes this in a special way:
"There were and still are many remarkable and amazing things about Voyager but to me the most remarkable was the timing. The planetary alignment that occurs only once every 175 years occurred at the time we were ready and able to do the mission. The necessary technologies were developed -- communications, navigation, power, electronics, attitude control, instruments. The scientists were experienced. There was strong public support. We could not have done it 5 years earlier and 5 years later the politics would not have supported it."
Right place. Right time. Bold ideas.
Next stop: Murmurs of Earth
Banner bus photo credit: Dorothy Delina Porter
