Heavens for Pennies: Voyager's Enduring Legacy

As NASA’s Voyager spacecraft explore the outer boundaries of the Solar System, transmitting vital data across billions of kilometres to the antennas of the Deep Space Network, their pioneering legacy throws into sharp relief a disturbing reality.
 
The forces of political and economic expediency, along with lurking indifference are threatening the grand human adventure of the Solar System and beyond. In the wake of a second year of proposed brutal budget cuts for NASA’s Planetary Science Division, Voyager 1’s impending date with the stars will be more than just a shift in cosmic ray and magnetic field patterns. This landmark event will serve as a symbol for the spirit of human curiosity, adventure and discovery, as Voyager becomes the first human emissary to the Milky Way.

Voyager2Carl Sagan stands near a model of the Voyager 2 spacecraft in January, 1986
Image credit: AP Photo/Lennox McLendon

Dr. Carl Sagan once wrote of the Voyager twins, “They came in at cost, on time, and vastly exceeded their design specifications––as well as the fondest dreams of their makers. Seeking not to control, threaten, wound or destroy, these elegant machines represent the exploratory part of our nature set free to roam the Solar System and beyond”.
 
For the past few years, both Voyager craft have been making their way through the tempestuous region of space known as the heliosheath. The heliosheath is the relatively narrow band of slowed and heated solar wind between the termination shock and interstellar space, the boundary of which marks the limit of our Sun’s charged particles. Voyager 1 entered the heliosheath in December 2004, followed by Voyager 2 in August 2007. From early 2009 to early 2012, Voyager 1 reported a steady increase in galactic cosmic rays, followed by a clear spike on May 7, 2012, suggesting an historic milestone was close at hand.
 

Voyager3Ed Stone with a Voyager model in 1972
Image Credit: NASA/JPL-Caltech

 In June, Dr. Ed Stone, project scientist for the Voyager program since 1972, stated with excitement, “The latest data indicate that we are clearly in a new region where things are changing more quickly… We are approaching the Solar System’s frontier.”
 
In December, it was confirmed that Voyager 1 had discovered a new region called the magnetic highway, where the Sun’s magnetic field lines connect to interstellar magnetic field lines. Voyager 1 is now truly living on the edge. “Although Voyager 1 still is inside the sun's environment,” Dr. Stone explains, “we now can taste what it's like on the outside because the particles are zipping in and out on this magnetic highway.”
 

Voyager5Voyager 1 Explores the 'Magnetic Highway'
Image credit: NASA/JPL-Caltech

Voyager 1, launched on September 5, 1977 from Kennedy Space Centre, is no stranger to attention. In 1990, for instance, the probe’s narrow-angle camera captured one of the most iconic images in space exploration history, now called The Pale Blue Dot. Requested by Dr. Sagan, who demonstrated a keen sense for its poetic implications, The Pale Blue Dot shows the Earth as 0.12 of a pixel amidst the vastness of space – a universal lesson in perspective.
 
Voyager 1 also discovered that one of Jupiter’s many moons, the Galilean satellite Io, is home to eight oxygen and sulfur-spewing volcanoes; and that Saturn’s enigmatic moon, Titan, has a nitrogen-rich atmosphere.
 
Voyager 2, which was launched on August 20, 1977, also made invaluable contributions to knowledge, including magnetic pole analyses of Uranus and the discovery of supersonic winds on Neptune.
 
All this exquisite knowledge and much more, cost each American citizen less than a penny a year from launch to reaching Neptune. Even within the heliosheath – the Voyagers are redefining scientific understandings – staying true to their reputation for discovery.
 
Data from both Voyager craft have allowed researchers to create computer models which demonstrate that the previously imagined smooth, streamlined look of the heliosheath is in fact a bubbly region of ‘magnetic foam’, created by magnetic field compression at the termination shock. Cosmic rays must make their way through this bubbly region before entering our Solar System.
 
Supplementing data from other craft, such as the Interstellar Boundary Explorer (IBEX) and Cassini, Voyager’s Interstellar Mission remains on the cutting edge of space exploration – many years after its Primary Mission ended. Remarkably, Voyager’s computer system is graced with a mere 8,000 bytes of memory.
 

Voyager4Voyager Spacecraft Instruments
Image Credit: NASA/JPL-Caltech

Whilst inevitably, as noted by Dr. Sagan, both craft are “destined to wander forever in the great ocean between the stars, the exact moment at which the Voyager 1 probe will officially enter interstellar space remains uncertain. Key indicators are being monitored closely.
 
The increase in galactic cosmic rays is only one of three data indicators that will ultimately confirm an interstellar breakthrough. When Voyager 1 pierces the true edge of the solar frontier, scientists expect intensity readings of energised particles (as experienced within the heliosphere) to drop off.
 
In addition, they predict the currently East-West oriented magnetic field lines to swing closer to North-South. Although the craft’s present environment is one of considerable magnetic intensity, the direction of the magnetic field lines have not changed. “The magnetic field data turned out to be the key to pinpointing when we crossed the termination shock,” says Leonard Burlaga, a Voyager magnetometer team member, “and we expect these data will tell us when we first reach interstellar space.”
 
Perhaps it is perfect timing that two spacecraft destined to eternally drift apart across the cosmos and whose operational longevity has always been uncertain, remind us of the raw guts and glory of boldly pushing frontiers and satisfying the ingrained human yearning for exploration.
 
The assault on NASA’s Planetary Science budget seems to be developing into an annual event. The 2013 Budget proposal would have slashed funding for the Planetary Science Division by 20%, including a 39% cut for the Mars Exploration Program. This prompted Dr. Neil deGrasse Tyson, on March 7, 2012 to warn Congress that, “NASA’s Mars science exploration budget is being decimated.” “It has come to this,” Nature reported two months later, “planetary scientists across the United States hawked baked goods to the public… in an effort to drum up awareness of their field’s dwindling financial support.”
 
The elite scientific minds of the world have been reduced to the peddling of cupcakes and washing cars. Equally strong protestations came from other scientists and space advocacy networks, including The Planetary Society, a group co-founded in 1980 by Dr. Sagan.
 
This combined public pressure (surely aided by the high profile landing of the Mars Science Laboratory Curiosity Rover in August 2012) resulted in Congress restoring $200 million to the final budget of March 2013. Now, the ‘annual assault’ starts all over again with the 2014 Budget, where The White House is launching another raid on the Planetary Science piggy bank, again calling for more than $200 million worth of cuts.
 
According to the Planetary Society’s latest petition, titled Write Congress to Save Our Science, Again, “The White House has doubled down on its efforts to cut Planetary Science at NASA. It's proposing a cut of over $200 million, despite the fact that Congress rejected a similar cut last year. This will prevent any mission to Europa. It delays for years efforts to send smaller spacecraft throughout the Solar System, and will have long-lasting repercussions on the scientific and engineering community.”
 

Voyager1The Voyagers in the Heliosheath (Artist Concept)
Image Credit: NASA/JPL-Caltech

Meanwhile, far away from the political storm, Earth’s most venerable and far-reaching spacecraft, the Voyager twins, continue relaying valuable scientific data after more than three decades of dutiful operation. Each time precious information is shot back to Earth across billions of kilometres of blackness, we are reminded that there is so much more to discover; so much more for which to strive.
 
As Voyager 1 soars towards the edge of interstellar space at 68,000 kilometres per hour, its transmissions still manage to inspire a handful of dreamers, who itch for the moment of interstellar breakthrough. Our knowledge of the Solar System and our place within it has been vastly expanded thanks to two small spacecraft that have traded us the Heavens for pennies.
 
Savor Voyager’s legacy and everything for which it stands, because the next time you stop at a set of traffic lights, a Planetary Scientist may be squeegeeing your windshield.