For most of the past year, the future of Brian Anderson’s experiments was up in the air—which is where the experiments will stay, thanks to the December bankruptcy bailout of Iridium LLC’s global satellite system. The fleet of 66 telecommunications satellites averted being deorbited when a new company, Iridium Satellite LLC, armed with a hefty contract from the Department of Defense (DOD), bought the $5 billion system for the token sum of $25 million.
With Iridium still aloft, Anderson, a space physicist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, can continue using onboard magnetometers—whose actual purpose is to keep tabs on satellite orientation—to watch how the solar wind drives Earth’s space weather.
From an hour’s worth of Iridium data, Anderson and colleague Colin Waters of the University of Newcastle in New South Wales, Australia, create snapshots of current flow in the northern polar region. Their data matches earlier maps pieced together from measurements taken over 18 months, and they have further shown that the currents change with the solar wind’s magnetic field, says Anderson. (They presented some of their early results at the American Geophysical Union meeting in San Francisco this past December.) Now they’re hoping to get more frequent data samples: “Solar wind activity varies on a scale of 20 minutes, so for storm monitoring we’d like to get down to a nine-minute refresh time.” Nine minutes is the time between two Iridium satellites on the same orbit passing a given spot.
“What users of space weather [data] really need is to fully characterize ionospheric current systems,” says John Kappenman, a division manager at Metatech Corp, which provides space weather forecasting to power companies. “How large are [the currents]? Where are they at any specific moment of time? Brian is demonstrating that you can move to a much more detailed depiction throughout the space environment. It’s a novel and elegant way of doing it.”
Combining their magnetic field data with electric field measurements collected by SuperDARN, a network of 12 ground-based polar radar antennas, Anderson and Waters also calculate that the Solar wind dissipates about 40 billion watts poleward of 60 degrees in quiet conditions. These calculations don’t work when the Sun acts up, however, since geomagnetic activity moves the current systems to lower latitudes, outside of Super-DARN’s range.
Indeed, a full view is one of the key advantages of piggybacking on the Iridium satellites, which encircle the planet at 780 km altitude. “It’s the first time we can watch these currents evolve through an entire storm. We are not limited spatially or temporally,” says Anderson.
But the piggyback ride nearly ended when the original owner, Iridium LLC, failed to attract enough users to its pricey telephone services. The new Leesburg, Virginia-based venture, Iridium Satellite LLC, chaired by Dan Colussy, a former president of Pan American World Airways, will seek mainly industrial and government customers. The bailout was made with the help of a $72 million contract from DOD, which buys the department two years of unlimited use for 20 000 people. DOD has its own gateway in Hawaii, and wants cryptographically secure phone service and global access for communicating in combat, polar, and remote areas. Iridium Satellite LLC has contracted with Boeing Co to run the satellites, and estimates total monthly operating costs of $7 million. “There certainly is risk involved—and a high one at that,” says Jose del Rosario, an industry analyst with the consulting firm Frost & Sullivan. “The potential is large, but it’s a slow market.” Still, the new company doesn’t have to recoup the original $5 billion investment.
Current flow in Earth’s northern hemisphere (as seen from above) derived from data from the magnetometers onboard the Iridium satellites. The currents flow up (red) and down (blue), parallel to Earth’s magnetic field. Upward flowing currents correspond to regions of auroral displays.
Current flow in Earth’s northern hemisphere (as seen from above) derived from data from the magnetometers onboard the Iridium satellites. The currents flow up (red) and down (blue), parallel to Earth’s magnetic field. Upward flowing currents correspond to regions of auroral displays.
