by Michael Benson
LJUBLJANA, Slovenia — In October 2003, the sun exploded with some of the most violent eruptions on record, spewing billions of tons of particles and gases into the solar system. These expulsions, which interfered with telecommunications on Earth and dosed the two astronauts in the International Space Station with multiple X-rays’ worth of radiation, gave clear evidence that the sun is nearing the end of a 22-year magnetic cycle.
A great deal was learned about these manifestations of solar rage because of a network of American spacecraft, all yoked together in a NASA division called the Earth-Sun System, which monitors the sun’s activity across the solar system. The very existence of such a network is one of those largely unsung achievements that confirm that we’re living in astronomy’s golden age.
Unfortunately, both the hard-won achievements and the future promise of this age are threatened by a shift by the United States toward a focus on crewed space missions over robotic ones, even though the latter have proved their worth, and cost-effectiveness, many times over.
An inspiring example of that are the most distant spacecraft in the Earth-Sun System, the twin Voyagers that provided us with the first detailed look at Jupiter, Saturn, Uranus and Neptune, as well as their moons and rings, in the late 1970s and through the 1980s. Now 11 billion and 14 billion kilometers (6.8 and 8.7 billion miles) away, the Voyagers are at the very edge of the sun’s domain; they’re the most distant artifacts of human civilization. When the solar eruptions finally reached Voyager 2 last April, its instruments determined that they had both merged and slowed. Thanks to the Voyagers and other spacecraft, we now know far more about how these “coronal mass ejections” form and dissipate. But this process isn’t over: The sun continues to rumble with unusual activity, and we’re in the excellent position of being able to monitor it with great precision.
As this story makes clear, although the Voyagers have been in flight for almost 30 years, they haven’t been kept operational out of nostalgia. Both have fully functional cosmic-ray, plasma-wave and charged-particle detectors, as well as other scientific instruments, and they have enough power to run them until at least 2020.
And they’re beginning to report phenomena unlike any detected before: plasma-wave oscillations and energetic particle activity that may indicate that they’re entering the “bow shock” region where the sun’s wind collides with the thin gas between the stars. The Voyagers, in other words, are on the verge of becoming the first true interstellar spacecraft, and give every indication of providing discoveries just as important as their previous ones.
But although these astonishingly hardy machines remain well equipped to continue their mission, their supporters are having a hard time defending them in NASA these days. In January 2003, President George W. Bush unveiled his “vision for space exploration,” which is almost exclusively about human spaceflight, and specifically about sending people to the Moon and to Mars. While some of these goals are worthy ones, they didn’t come with a budget increase in keeping with their ambitions, and recently NASA quietly excised some of its longest-running robotic missions from this year’s budget – including the two Voyagers.
Some hold out hope that the incoming NASA administrator, Michael Griffin, will reverse this decision. But it’s hard to imagine Griffin, an ardent advocate of crewed spaceflight, doing so, at least in the current fiscal climate, without direct congressional intervention.
Along with the self-destructive decision to cancel a shuttle mission to maintain the Hubble Space Telescope, which will die in orbit within the next couple of years without servicing, the moves on the Voyagers and other Earth-Sun System spacecraft give clear indication that astronomy’s golden age is in danger of ending not with a bang, but with a series of whimpers – death by a thousand budget cuts.