A million miles from the earth, NASA's Advanced Composition Explorer (ACE) spacecraft suddenly found itself under assault. Late in January, the tiny, instrument-packed spacecraft was buffeted by an exceptionally powerful burst of particles spewed out by the sun. In the space-environment control room at the National Oceanic and Atmospheric Administration (NOAA) headquarters in Boulder, Colo., alarms sounded. "All of a sudden, a blast wave of solar wind showed up at the ACE spacecraft," says NOAA's Joe Hirman, "as dense as any we've seen, and, bam, 30 minutes later the earth's magnetic field got hit hard."
A few days earlier, the Solar and Heliospheric Observatory (SOHO), high above the earth, had captured images of another solar phenomenon--an unusually large prominence, a loop of fiery gases 800,000 miles wide, erupting from the sun's surface. It was also recording increasing numbers of flares--exceptionally hot blotches on the solar surface--and a proliferation of sunspots migrating inexorably toward the sun's equator.
To astronomers, such events signal an approaching solar maximum, a period of great turbulence that roils the sun every 11 years or so. The last solar max occurred in 1989. Now the sun, right on schedule, seems headed toward a peak of activity later this year.
During solar maximums, space weather becomes stormy. The normally benign sun pounds the earth mercilessly with ultraviolet radiation, X rays and floods of charged particles, distorting the planet's protective magnetic field and inducing powerful electric currents that can wreak havoc not only with spacecraft but also with many aspects of terrestrial life.
One 1989 solar storm knocked out Hydro-Quebec transformers, leaving 6 million people in eastern Canada and the U.S. Northeast without electricity for nine hours. The same storm disrupted shortwave radio transmissions, crippled Coast Guard loran navigation systems and had automatic garage doors opening on their own.
In the years since, we have become increasingly dependent on satellite-based communications, and even off-peak solar outbursts have caused trouble. They are suspected in damage to at least a dozen satellites, and the failure of the Galaxy IV satellite during a 1998 solar storm that silenced 80% of North America's pagers. In the past four years alone, says Chris Kunstadter, of U.S. Aviation Underwriters, space losses may have exceeded $550 million.
Since the last maximum, the number of satellites in orbit has increased sixfold, to more than 600. They are essential for everything from telephone service and air-traffic control to you-name-it.com connections, pay-at-the-pump credit-card service and hundreds of other information-age conveniences. Yet for reasons of economy, or just plain indifference, few of these spacecraft are properly shielded.