In the middle of a snow-draped forest in Alaska, a long four-hour drive east from Anchorage, sits a cleared 30-acre field where 180 silver poles sprout from the ground and reach 22 meters into the air. During four nights this week the poles—actually interconnected radio antennae—will spring to life after three years of dormancy, and heat the highest wisps of our atmosphere directly above.

The antennas belong to the High Frequency Active Auroral Research Program (HAARP), a former U.S. military facility near the hamlet of Gakona. The array will beam 2.1 megawatts of radio energy into the ionosphere—the region that starts at 100 kilometers above the ground, where solar photons and charged particles crash into Earth’s atmosphere. There the radio signals will excite electrons and turn them into waves of relatively hot ionized gas, or plasma, in a narrow slice of sky. The hope is to better understand activity that hampers satellites as well as some elusive features of radio wave physics.

The antenna forest was originally funded by the U.S. Navy and Air Force to improve their navigation and communication signals bouncing around the planet. Since its first transmissions in 1999, however, it has been accused of doing much more. Iran blamed HAARP operations for floods, the late Venezuelan leader Hugo Chavez charged it with triggering 2010’s devastating Haiti earthquake and legions of other conspiracy theorists have accused it of everything from mind control to stealing souls.

In fact the only thing the military was interested in controlling was the hot plasma, says Bill Bristow of the University of Alaska Fairbanks, who is HAARP’s chief scientist. The plasma can distort or delay satellite transmissions and GPS signals. The armed services wanted to know whether those perturbations could be manipulated from the ground to eliminate such problems, and perhaps enable new communications and radar technologies. So they built HAARP, the world’s most powerful ionosphere heater.

More than a decade of experiments, however, failed to produce any major breakthroughs. Eventually the military threw in the towel. In 2014 David Walker, then deputy assistant secretary of the Air Force for Science, Technology and Engineering, told a Senate committee, “If there is not somebody who wants to take over the management and the funding of the site…we plan to do a dismantle of the system.”

The pending demise caught the attention of scientists at U.A. Fairbanks’s Geophysical Institute. “We felt that there was a large investment of public money that should not just be destroyed,” Bristow says. “There’s a lot of scientific work yet to be done, so we wanted to give it a go.” The Air Force officially handed over HAARP’s keys to the institute in 2015.

Now after years of repairs, upgrades and fund-raising, HAARP is about to embark on its first scientific campaign under civilian control. Much of the work is a continuation of studies that began under the military. Plasma scientists, for example, will hunt for an elusive phenomenon called two-plasma decay instability. This involves an electromagnetic signal decaying into two electron plasma waves. Understanding this instability is key to some experimental nuclear fusion reactions but it has never been observed for high-frequency radio waves.

The facility is also going to be generating artificial aurorae. At full power, HAARP’s transmitter can produce a glowing plasma high in the sky that, although not as bright as the natural aurora borealis, is visible to the naked eye. Producing artificial aurorae has taught scientists unexpected lessons about how gases are ionized in the ionosphere, a process that helps protect Earth from harmful ultraviolet solar radiation. “Understanding how energy from the sun flows into the upper atmosphere is important for understanding the effect on Earth from extreme solar events,” Bristow says.

And the military could not quite let go of HAARP altogether. The Naval Research Laboratory thinks it can use the ionosphere to improve spy satellite operations. The lab will be running an experiment where it bounces radio signals off the ionosphere and then back down to the sea, hundreds of kilometers over the horizon. Satellites overhead will then try to use the radio reflections from the ocean surface to detect ships or ice. Because the satellites will rely on the facility’s signals, and not their own, this method could enable them to stay cloaked from prying eyes and conserve their own energy.

The success of these initial experiments will be critical in demonstrating the long-term viability of HAARP to the agencies funding the efforts along with the navy: the National Science Foundation and U.S. Department of Energy. “This beauty of HAARP is that it’s a way to turn the ionosphere into a plasma lab where we can control the knobs and timing,” says Mark Moldwin, a professor of space sciences at the University of Michigan who is not involved with the current research. “It has essentially come back from the dead and the community is hopeful that its continued operation will enable education and research opportunities.”

U.A. Fairbanks says it will support the facility for about two more years. Then it could pull the plug if more sponsors are not forthcoming. But for the week ahead the biggest risk is nature itself, Bristow says: “If it’s cloudy, we won’t see the auroras, and a solar storm could wipe out our ability to do any heating at all.” There is nothing the facility can do about clouds and storms. Despite the rumors, Bristow says, HAARP has never been able to control the weather.