NASA confirmed an incredible discovery Tuesday - that an amateur radio astronomer, on the hunt for a classified government satellite, stumbled instead upon signals from a spacecraft that had been thought lost 12 years earlier, raising hope that NASA can resurrect a mission that changed our understanding of the "invisible ocean" around the Earth.

IMAGE was a machine designed to "see the invisible," as one of the mission's lead scientists once put it.

It was a squat and boxy thing, like many satellites, with a long technical name - Imager for Magnetopause-to-Aurora Global Exploration - that obscured its plain and noble purpose: to map the roiling sphere of electric gas around the Earth that protects us from the sun, and which we had never seen in full before.

Before IMAGE launched in 2000, humans had known only for a few decades that a magnetosphere surrounded the planet.

In an essay before the launch, the mission's lead investigator, James L. Burch, called it an "invisible ocean . . . where nothing tangible - no snow or sand or tree or even a cloud - records titanic currents and pulses."

The sphere shields our planet from the sun's harsh winds while letting through its light. Like an ocean, its plasma flows and ripples in a solar breeze.

But also like an ocean, it is prone to storms - solar disruptions so violent they can knock out satellites and even power grids on Earth.

IMAGE was built, Burch wrote, to send home images of the global magnetosphere for the first time in history and help predict those storms.

For five years, it astonished us.

The satellite beamed back pictures of an enormous solar storm in the summer of 2000 and allowed scientists to essentially live-stream "weather" in space. The sphere around the Earth proved to be a much stranger place than had been thought.

IMAGE discovered that the Earth spits out jets of its own atmosphere to defend itself from space storms - like a squid shooting ink - the Dallas Morning News wrote in 2002.

It discovered cracks in the Earth's magnetic field, tracked down the source of mysterious radiation and imaged 100,000-volt charged particles whipping around the circumference of the globe.

And in the last month of 2005 - on the same day the US president addressed the nation from the Oval Office, promising an end to a still-young Iraq War - IMAGE stopped sending pictures. The satellite had suddenly gone invisible itself.

The scientists tried to figure out why. A tripped breaker in the radio was their best guess. But without a radio, they couldn't tell it to turn itself back on.

After a month of silence from IMAGE, NASA published a news release that declared the satellite's mission a great success - one that was now over.

"The craft's power supply subsystems failed," the agency wrote, "rendering it lifeless."

NASA was wrong. IMAGE was not dead, but it would circle Earth for more than a decade before a man with no professional astronomy training - one who did not always accept the official explanation of events - heard its call.

The 21st century moved into its second decade, and space exploration changed. New machines were sent into orbit, and some of them, like IMAGE, were lost too.

In the first month of 2018, an unknown government agency used a private company to launch a secret satellite, code-named "Zuma". It was nothing like IMAGE; it was a machine intended to be invisible to most of the world.

And it failed immediately.

No one has said publicly what, exactly, went wrong during the January 7 launch, whether Zuma crashed back into an ocean or simply died in space.

Its fate and purpose have become a mystery of the new Space Age - and all of this bothered Scott Tilley very much.

Tilley is a 47-year-old electrical engineer who lives on the west coast of Canada. His hobby is radio astronomy. In a sense, it's also his cause.

"Space is not owned by anybody," Tilley told The Washington Post. "Anybody should be able to look up and know those little dots moving across the night sky are not bombs."

Secret military satellites and classified orbits bother him, so he has banded together with a small group of fellow amateurs across the world to to track down every satellite whose operators don't want it to be seen.

Maybe Zuma was in pieces underwater, Tilley thought. But maybe not. So he began to scan. He used no telescope, listening instead for radio signals out there, in the invisible ocean.

When Tilley caught a signal after a week of searching, on January 20, he almost ignored it. Whatever it was, it was orbiting much higher than Zuma was supposed to be.

There are hundreds of active satellites in space, most of which didn't interest him. "I didn't think of it much more," he wrote on his blog.

But as he continued to scan for Zuma, he came across the signal again - stronger this time - and out of curiosity checked it against a standard catalogue.

The signal matched for IMAGE. But IMAGE was supposed to be dead.

Tilley had to Google the old satellite to find out what it was, as it had been all but forgotten on Earth. Eventually, he came across a decade-old NASA report on the mission's failure.

"Once I read through the failure report and all the geeky language the engineers use, I immediately understood what had happened," Tilley told Canadian Broadcasting Corp. News.

Then he rushed to contact NASA himself.

That old news release announcing the death of IMAGE had not actually been the end of its story on Earth. A week later, in early 2006, NASA quietly convened a board of experts to pore over the satellite's entire data set and figure out what went wrong.

They worked for months. When their final report was released, the board still figured IMAGE had tripped a power breaker and essentially bricked itself, like a bad iPhone.

But they had come up with a theory for how the satellite might be fixed. Or rather how it might fix itself.

IMAGE was solar-powered and designed so that if its battery ever drained enough, it would try to reset its computer and flip the breaker back.

The board thought this was most likely to happen in late 2007, when IMAGE's orbit would put it in the Earth's shadow from the sun - from the satellite's point of view, a deep eclipse.

The theory didn't pan out. When NASA tried to the contact IMAGE after the eclipse, it remained as silent as ever, so the agency closed down the mission for good.

And then, a decade later, Tilley found the machine chirping away.

After his discovery, another independent astronomer, Cees Bassa, looked for IMAGE's signal in years of old data. He hypothesised that while the 2007 eclipse didn't manage to reset the satellite, another one did the trick, probably sometime between 2014 and 2016.

"Most likely the battery efficiency degraded such over the IMAGE lifetime that during the less deep eclipses the battery drained sufficiently to lead to the reset and bring the transmitter aboard IMAGE back to life," Bassa wrote.

NASA hasn't confirmed that. In fact, the agency was initially skeptical that the signal Tilley found actually came from IMAGE.

After Tilley contacted NASA last week, scientists trained antennas at the Goddard Space Flight Center on the object. Initial tests showed its orbit, frequency, oscillation and spin rate all matched their old, lost satellite.

Even so, NASA was cautious in its public updates, writing Sunday that it still wanted to analyse the signal's encoded data before it could be sure.

Meanwhile, astronomers amateur and professional were getting excited. "The team is collectively holding their breath," Patricia Reiff, an investigator on the original mission, told Science Magazine.

On his blog, Tilley quoted from an email sent to him by Burch, the lead investigator on the IMAGE mission, who wrote so many years ago of a machine to map an invisible sea.

"Very excited," Burch wrote to Tilley.

Confirmation finally came Tuesday. It came couched in the technical jargon of space science and was no less momentous for it.

"On the afternoon of January 30, the Johns Hopkins Applied Physics Lab in Laurel, Maryland, successfully collected telemetry data from the satellite," NASA wrote.

"The signal showed that the space craft ID was 166 - the ID for IMAGE.

"The NASA team has been able to read some basic housekeeping data from the spacecraft, suggesting that at least the main control system is operational."

Translation: There is hope that IMAGE will one day tell us more about the "ocean" it's been adrift in for more than 12 years.

"I really hope the scientists who built this thing and put it in space are able to repurpose this and put it back into action," Tilley told CBC News. "And we get the benefit of all the beautiful science coming home."

He was named nowhere in NASA's news release, except as an anonymous "amateur astronomer."

That's fine. He knows he found the thing, when the professionals might have left it in the dark forever.

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This article was originally published by The Washington Post.