25th August 2012 was a day like any other.
A few would have celebrated their birthdays and anniversaries. A few would have marked the day with a grand celebration while some others would have longed for the seemingly interminable day to end. But for most of us, it was a rather unremarkable day.
The truth that eluded us all, however was that, as we were trudging through the daily mundane as individuals - marking our minor successes and our failures - humanity as a collective had done something truly remarkable.
On this very day, a journey that had begun nearly four decades ago had finally come to fruition. We had finally reached the edge of our cosmic back-yard. The twin voyagers had finally left our solar system and were now truly in the "beyond" - in the unknown that has enthralled us since our very beginnings.
Having been born after the golden era of space exploration, many in my generation have probably spent their early years quite oblivious to the wonders of outer space and the marvels of space missions. That indifferent, almost juvenile attitude to all-that-was-before-me has thankfully left me over the years and has evolved into a strong fascination for science and an appetite for history. As a project that evolved with the times and made the most efficient use of resources, the Voyagers are a prime example of a brilliant scientific mission - well planned, flexible and hugely successful.
The twin spacecrafts of Voyager 1 and 2 were launched by NASA in separate months in the summer of 1977 from Cape Canaveral, Florida. They were originally designed to last five years to conduct close-up studies of Jupiter and Saturn, Saturn's rings, and the larger moons of the two planets. But as the mission went on, the project was expanded to include additional fly-bys of Uranus and Neptune - outermost giant planets of our solar system. As the years rolled by and the spacecrafts flew across the solar system, they were reprogrammed by remote control and endowed with greater capabilities than what they possessed at the start of the mission. In due course, the five year lifetime of the mission was first stretched to 12 and then to more than three decades; and the two-planet mission became a huge four-planet mission. After careful consideration of more than 10,000 possible trajectories, two were shortlisted for their ability to gravity-assist and to permit the possibility of extending the mission to include Uranus and Neptune.
The mission itself was rather cleverly designed to take advantage of the rare geometric arrangement of the planets in the late 1970s and 1980s which allowed for the ambitious four-planet tour with a minimum of propellant and trip time. This rare layout of the planets Jupiter, Saturn, Uranus and Neptune occurs about once in 175 years and allowed the voyagers to adopt a flight path that would allow them to swing from one planet to the next without the need for large onboard propulsion systems. The flyby of each planet would bend the spacecraft's path and increase its velocity enough to deliver it to the next destination.
Image courtesy JPL
After their launch in the summer of 1977, Voyager 1 reached Jupiter on March 5, 1979 and Saturn on November 12, 1980; while Voyager 2 reached Jupiter on July 9, 1979 and Saturn on August 25, 1981. After their individual successful missions, it was shown that Voyager 2 could likely continue flying to Uranus with all instruments operating and thus the additional missions were added onto the original project.
After their encounters with Uranus and Neptune, the Voyagers continued their journey outwards from our solar system. Since then, both Voyager 1 and 2 have been hurtling out of the solar system at 520 and 470 million kilometers a year giving us the very first views of our cosmic back yard. For nearly two decades since then scientists have been listening to the outside world through the Voyagers and the inevitable exit from the Solar system into the interstellar space has been keenly anticipated.
After sending us breathtaking shots of Neptune and Uranus, the Voyagers continued to swim through a sea of plasma particles in the ever-expanding solar wind before encountering the sudden termination shock. Here the solar winds slow down from super-sonic to sub-sonic speeds and massive changes in the flow of plasma and magnetic fields are seen. Voyager 1 crossed the termination shock to enter the heliosheath in 2004 while Voyager 2 crossed it three years later in 2007. The heliosheath is the outermost edge of the solar system and its thickness was an unknown to us. Hence ,the signals from the Voyagers were closely monitored to detect the end of the sun's influence.
For a little more than half a decade now, the Voyagers have been hurtling towards the outer edge of our Solar system in search of the Heliopause, where as the name suggests, the influence of our fireball-sun wanes and the beginnings of the interstellar space can be sensed.
Image courtesy NASA/BBC
This milestone was finally reached on 25th August 2012, when based on the change in solar winds, charged particles and plasma waves, it finally seemed that the Voyagers had crossed over. But we wouldn't know of it until last week when scientists were finally able to confirm the exact date and the transition based on all the data that had been sent by the Voyager.
Having exited our solar system, the voyagers continue to move away from us at alarming speeds. They are estimated to have enough electrical power and thruster fuel to operate atleast until 2020 by which time they should be more than 10 billion miles away from the Solar system. Eventually however, the power systems will shut down and the Voyagers will be left to drift in space. And in about 40,000 years, Voyager 1 will drift within 1.6 light years of a star (AC+ 79 3888) in the constellation Camelopardalis while voyager 2 will be 1.7 light years away from another star Ross248. In about 296,000 years, Voyager 2 will pass within 4.3 light-years of Sirius - the brightest star in our sky. We, as a species will never know of it and may not even be here to witness it.
The Voyagers now lie beyond the influence of our solar system and in the realm of the stars. With them flies a slice of humanity in the form of the Golden records. After their success with the Pioneers 10 and 11 which preceded the Voyager, NASA decided to place a more ambitious message - a time capsule, aboard the Voyagers. Intended for the benefit of any spacefarers, the capsules were designed to communicate a story of our world and its people. Although the intended communication with the extra-terrestrials may never happen, the idea of encapsulating all of humanity on a phonograph record is much more romantic.
And thus long after we lose contact with them, and perhaps long after we ourselves may last, the Voyagers and with them, a sliver of humanity - will continue to drift away, eternally in the milky way. Recorded on a 12 inch gold plated copper dish, the Voyager message contains sounds and images selected to portray the diversity of life and culture on earth. The contents of the golden records were selected for NASA by a committee lead by Carl Sagan. The discs included 115 images detailing life on earth including images depicting human physiology and reproduction. They also included sounds of surf, wind, thunder, birds, whales, musical selections from different cultures and eras, greetings in 55 different languages and printed messages from the then American President Jimmy Carter and the UN Secretary General Waldheim. On the subject of the record, Carl Sagan noted, "The spacecraft will be encountered and the record played only if there are advanced civilizations in the interstellar space."
While the prospect of extra terrestrials encountering humanity is rather exciting, more poignant are Sagan's next few words - "Launching of this bottle into the cosmic ocean says something very hopeful about life on this planet."
Image courtesy JPL
Although the Voyagers are a great symbol of our scientific prowess, they represent a lot more than that. There is something mystical and powerful in sending out a representation of us as a species - into the unknown. The Voyagers are custodians of that sliver of humanity that is floating between the star dust even as I type these words. And tomorrow, even if the human race burns itself and this planet to the ground, somewhere out there, there will be a piece of us, hurtling through space, wandering through the cosmos.
Unlike most of science and technology that fills us with a sense of hubris - of having reached where no one before has, of doing what has never been done, the Voyagers make us feel grounded and connected. As Sagan beautifully said, "We are like butterflies who flutter for a day and think it is forever."
It is events like this that remind us of the true scale of things. The Voyagers are like a prayer of hope cast out into a stormy sky. They are a symbol of our competence and a proof of our existence - and yet they make us seem inconsequential in the grand scheme of events. To me there is grandeur in this view of life - a sense of being and a sense of belonging.
References:
1) http://www.bbc.co.uk/news/science-environment-24026153
2)http://www.smithsonianmag.com/science-nature/What-Is-on-Voyagers-Golden-Record.html
3)The Jet Propulsion Laboratory Website: http://voyager.jpl.nasa.gov/mission/interstellar.html
4) http://www.bbc.co.uk/news/science-environment-24026153
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