It’s not often that a scientific discipline gains a 23-satellite constellation overnight. But today, space weather scientists are reaping such a windfall, as the Los Alamos National Laboratory in New Mexico has released 16 years of radiation measurements recorded by GPS satellites.
Although billions of people globally use data from GPS satellites, they remain U.S. military assets. Scientists have long sought the data generated by sensors used to monitor the status of the satellites, which operate in the heavy radiation of medium-Earth orbit and can be vulnerable to solar storms. But few have been allowed to tap this resource. “There’s a general hesitancy to broadcast even fairly innocuous things out to the broad community,” says Marc Kippen, a program manager at Los Alamos, which developed the radiation-measuring instruments.
That attitude changed in October 2016, when the outgoing Obama administration issued an executive order aimed at preparing the country for extreme space weather. Such bursts in charged particles, originating in a solar flare or coronal mass ejection, could disable the electrical power grid or divert flights away from the Arctic, where radiation exposure is heightened.
The GPS data, which dates from December 2000, fill a hole in studies of space weather, the complex interplay of Earth’s magnetic field with bombarding radiation from cosmic rays and the sun. These satellites operate exposed to the Van Allen belts, two donuts of highly energetic radiation wrapped up in Earth’s magnetism. Although purpose-built spacecraft, like NASA’s Van Allen probes, have studied the belt, nothing can beat the GPS system for the frequency and duration of its observations, according to Steven Morley, a Los Alamos researcher.
For example, Morley and his peers have used data from seven satellites to track a steep loss in the flow of energetic electrons, during a May 2007 solar wind, in less than 2 hours. “Faster than anyone thought the losses could happen,” he says. They went on to show that a certain kind of solar wind, called a “corotating interaction region,” can predictably be shown to drive such losses in the radiation belt. The data, which measure electrons and protons, have also been shown to match well with existing purpose-built instruments, he adds. “We’ve shown we’re measuring the overall picture to very high fidelity.”
This release should be emulated by other nations as they invest in space-based navigation systems, says Delores Knipp, a magnetosphere researcher at the University of Colorado in Boulder and the editor of Space Weather, which released an explanation of the GPS instruments today. Having such data, she adds, “is crucial to learning how these particles influence our upper atmosphere all the way down to aviation altitudes.”
The GPS data, available by searching for “GPS energetic particles” on data.gov, have their limits. In particular, they can’t tell the direction of the particles striking them. But the Los Alamos team hopes scientists will use the data to build better models for predicting solar storms.
*Correction, 31 January, 10 a.m.: A previous version of the story incorrectly stated that corotating interaction regions were shown to supercharge the radiation belt.