The false alarm happened in 1997.

The Green Bank Radio Observatory in Green Bank, West Virginia, was picking up some unusual signals—and Seth Shostak, then the head of the Center for Search for Extraterrestrial Intelligence (SETI) Research in Mountain View, Caifornia, was convinced that they had come from intelligent life somewhere in the universe.

“It looked like it might be the real deal,” Shostak recalled. Within a few hours, he had a call from The New York Times.

But within a day, it became clear that the source of excitement was actually a European satellite. To make matters worse, a second telescope in Georgia, which would have told the scientists about the true nature of the signal, wasn’t working.

Yet Shostak says that false alarm proved to be a valuable dry run for the astronomers, giving them a small taste of what would happen if the signal turned out to be real. In 1989, the International Academy of Astronautics adopted its SETI Post-Detection Protocols, a set of guidelines for how to proceed once intelligent life is discovered among the stars. SETI researchers hope that one day soon, they’ll have a chance to use them.

Later this month, the 100-Year Starship Project (100YSS), a NASA-funded initiative dedicated to achieving interstellar travel within the next century, will discuss the lessons to be learned from the 1997 incident during its annual symposium, this year with the theme “Finding Earth 2.0.”

Since the first exoplanet was identified in 1992, astronomers have confirmed the existence of nearly 1,900 planets beyond our solar system. The sheer number of planets increases the statistical probability that Earth-like planets will be found. Some estimate that there are around 140 habitable planets in our stellar neighborhood within 33.6 light years of Earth. Many astronomers estimate that we’ll find a life-bearing planet within 25 to 30 years, or maybe tonight, if we know what to look for.

The upcoming 10YSS symposium will focus on both the pragmatic and more theoretical elements of such a discovery: How do we find Earth 2.0? How do we confirm evidence of life? If we find evidence of intelligent life out there, how do we announce it to the world? How will the people of Earth 1.0 react?

“How do you finally decide, ‘Eureka, we found it?’” said Mae Jemison, a former NASA astronaut and the principal for 100YSS. “What are the compelling signs of finding another planet outside of our solar system that indisputably is terrestrially evolved, with earth-like evolved lifeforms? …  What would happen if we could identify it [as Earth 2.0]? How does that change us?”

Jill Tarter, a former director of the Center for SETI Research who was present at the Green Bank observatory during the 1997 incident, said the first and most important step is to verify that a suspected signal from an intelligent source is indeed from another star system. “We worry, being in California, about all those post-graduates and Caltech students deliberately trying to fool us simply because they can,” said Tarter. Before any public announcement, “it should get verified independently” so as not to undermine SETI’s credibility.

The radio signal they’re looking for will stand out from cosmic radiation background noise—but so do signals from satellites, ground interference, and possibly natural but unknown astronomical phenomenon. If the signal occupies only a narrow band of frequencies, however, that separates it from natural cosmic emissions, suggesting a deliberate signal. Turning the radio telescope’s dish slightly from the signal’s apparent source can determine its distance:  If the source is nearby, the signal will slowly fade. If it’s coming from a distant star, the signal will drop off sharply.

If all signs indicate that the signal is coming from another star, the astronomers contact other observatories or research organizations that subscribe to the Post-Detection Protocols to confirm a) that the signal exists, and b) that it’s likely coming from an intelligent source. If the other groups confirm the the signal, the original astronomers sound the alarm, alerting their national authorities of the discovery and sending an International Astronomical Union “telegram”—these days, an email—to observatories around the world. The guidelines also account for the United Nations’s 1967 Space Treaty, which calls for member states to notify the U.N. of their space-exploration activity—under the Protocols, the discovering astronomer alerts the Secretary General to the discovery, as well as a number of other international bodies.

Once all this is done, the astronomer who discovered the signal also has the privilege of making the first announcement to the public.

At least, in theory. Most likely, Shostak believes, the news would leak well before any official announcement. In his memoir Confessions of an Alien Hunter, he recalled how The New York Times knew about the 1997 false-alarm signal:

Much later, I figured out how [the New York Times reporter Bill Broad] had learned of the detection. Broad had been working on a biographical story of Carl Sagan, who had died six months earlier. As part of the effort he called Sagan’s widow, Ann Druyan. Her secretary had already been in touch with Christine Neller, looking for Jill Tarter. The secretary was told that Tarter was still in West Virginia, postponing her flight to check out a signal. That innocuous tidbit was passed to Druyan, who passed it to Broad, who called me. There is no secrecy in SETI.

“The protocols are as much fiction, in some sense, as the movie portrayals. The story will break in a very messy way,” he said. “I don’t think there’s any way to control the media.” Not that he necessarily wants one—the Protocols call for any confirmed detection of an extraterrestrial signal to be “disseminated promptly, openly and widely through scientific channels and public media.”

“You want that information to be as widespread as possible,” Tarter said. “If we were to make a discovery at the SETI institute, I don’t think there’s any way we could keep our website up or our phones working from the onslaught of people trying to get information.”

If managing the news media is impossible, so is managing the public’s reaction to the news of the discovery of life out there.

Paul Ziolo, a professor of psychology at the University of Liverpool and a regular presenter at the 100YSS symposiums, points to the film Contact, based on Sagan’s novel, as an accurate depiction of the disparate emotions that could result from such a discovery. “It’s a massive range from paranoia to jubilation to despair,” Ziolo said. “For some people, anything from outside is going to threaten power structures. For others, it’s the gods they’ve been waiting for.”

For Tarter, who Sagan used as one source of inspiration for the lead character in Contact, any discovery of intelligent life out there gives us hope for our own future.

“If we succeed at detecting another technological civilization, that success helps tell us that on average, technological civilizations can survive for a long time,” she said. “The very act of success [in hearing from another planet] tells us that we can have a long future. I think that’s the most amazing impact that contact would have, even if we never figure out how to interpret whatever information we receive.”