(Hear Nadia Drake interviewed live about the Arecibo telescope on Science Friday from Public Radio International, on Friday June 10 at 2 p.m. EST/11 a.m. PST.)

Tucked into a sinkhole in the Puerto Rican jungle, the world’s largest single-dish radio telescope scans the skies for signs of distant galaxies, elusive gravitational waves, and the murmurs of extraterrestrial civilizations nearly 24 hours a day. For more than a half-century, whether those waves traveled to Earth from the far reaches of our universe or much closer to home, the Arecibo Observatory has been there to catch them.

But the enormous telescope, with a dish that stretches 1,000 feet across, may not be around for much longer.

On May 23, the National Science Foundation, which funds the majority of Arecibo’s annual $12 million budget, published a notice of intent to prepare an environmental impact statement related to the observatory’s future.

That might sound innocuous – after all, isn’t it a good idea to study the context in which our science facilities exist? Yet it’s anything but benign. Putting that environmental assessment together is a crucial step NSF needs to take if it plans to yank funding from the observatory and effectively shut it down.

“It appears that NSF is following the formal process established, in part, by the National Environmental Policy Act of 1969, for decommissioning of a federal facility,” says Robert Kerr, former director of the observatory. “The good folks at Arecibo are scared to death.”

The decision to close Arecibo hasn’t been made yet, but the move follows an ominous drumbeat of similar announcements and reports that have accumulated over several years, most urging NSF to send its resources elsewhere. Now, options for Arecibo’s future range from continuing current operations to dismantling the telescope and returning the site to its natural state. It’s a decision NSF hopes to make — with input from the public — by the end of 2017, says Jim Ulvestad, director of NSF’s Division of Astronomical Sciences.

View Images Above the 1000-foot dish, a 900-ton platform is suspended from three tall towers. (Nadia Drake)

The most extreme option, which could include explosively demolishing the giant dish, might affect such things as ground water, air quality, and ecosystems – thus the importance of studying the environmental impact of potential futures, especially ones that involve shutting the telescope’s eyes.

“On a practical level, the telescope would in time — perhaps a short time, given the tropical site — become very unsafe,” says Cornell University’s Don Campbell, a former observatory director. “Short of permanently guarding it, deconstruction would be necessary.”

Not surprisingly, this notice of intent is causing significant concern among astronomers and the local community. Arecibo is the most sensitive radio telescope in the world; and despite its age, it’s still involved in world-class science, like the search for gravitational waves. Importantly, it also helps boost a sagging local economy, and has inspired many Puerto Ricans to pursue science and think about the mysteries of the universe.

“Puerto Rico feels a sense of ownership and pride for the observatory,” says Emmanuel Donate, an astronomy graduate student at the University of Georgia who started a petition to keep the observatory funded. “I consider using it, especially in person as I’ve been doing the last couple weeks, one of the highlights of my life and a tremendous personal honor.”

A Tropical Icon

Construction at Arecibo began in 1960, when – among other things – the U.S. government wanted to find out if Soviet ICBMs could be detected using charged particles in their atmospheric wakes. The telescope didn’t work well at first, but after a few upgrades it was the most sensitive cosmic radio wave detector in the world. That’s not it’s only trick, though: In addition to collecting photons from space, Arecibo is also capable of sending radio waves into the cosmos, a talent scientists use to scrutinize potentially catastrophic asteroids on Earth-crossing orbits.

View Images The Arecibo Observatory, as seen on Google Earth.

In the intervening decades, Arecibo has been involved in loads of top-notch science, including work that was awarded a Nobel Prize. But it’s also become a recognizable symbol of humanity’s quest to understand our place in the cosmos (my dad, a former observatory director, used Arecibo to send Earth’s first intentional postcard to the stars in 1974), and is a semi-frequent character in popular films and TV series, including The X-Files, Contact, and GoldenEye.

To say the telescope is iconic is not an overstatement.

Stormclouds on the Horizon

But a frustratingly flatlined budget is forcing the National Science Foundation to ration its resources. To do that, NSF relies on a somewhat contorted process of soliciting input from external reviews and panels, federal advisory boards, and the National Research Council’s decadal surveys, which prioritize science goals for the coming decade.

“NSF, like most federal science agencies, has much more worthy science proposed to it than it is able to fund,” Ulvestad says. “Within the constraints of its resources, NSF responds as well as possible to those community and governmental science priorities and recommendations.”

The most recent decadal survey, published in 2010, prioritized science requiring new facilities instead of experiments that could be conducted at places like Arecibo. That survey, in combination with the dismal funding situation, is what’s causing NSF to look for facilities to dump.

View Images Arecibo’s dish is suspended above the floor of the natural depression it sits in. Beneath it, plants grow like crazy. (Nadia Drake)

Despite its iconic status, Arecibo is an easy target – newer, shinier telescopes are coming online, and it’s got a relatively small number of users compared to optical telescopes across the United States, many of which are individually less expensive to run.

Over the past decade, multiple panels have called for severe reductions in funding for the observatory, starting with a 2006 NSF review that recommended finding alternative sources of cash for Arecibo. “The [senior review] recommends closure after 2011 if the necessary support is not forthcoming,” the report says. “This raises the important question of the cost of decommissioning the telescope, which could be prohibitively large.”

That review was followed by a 2012 assessment of the facilities funded by NSF’s astronomical sciences division. While somewhat less gloomy – the committee recommended keeping the observatory in NSF’s portfolio – the 2012 panel suggested revisiting Arecibo’s funding status later in the decade, “in light of the science opportunities and budget forecasts at that time.”

NSF followed that review with a 2013 letter saying it would begin studying the costs and impact of decommissioning the giant telescope – a matter that would be complicated by the telescope’s history and location in a region of high biodiversity, “thus these reviews should be started as soon as practicable.”

The cloudy outlook intensified this year, when NSF’s Astronomy and Astrophysics Advisory Committee urged the agency to proceed with divestment “as fast as is practical.” That was quickly followed by another NSF review that advised a 75% reduction in funding from the agency’s Atmospheric and Geospace Sciences division (AGS), slashing contributions to atmospheric research from $4.1 million to $1.1 million.

And now, the sky is looking dark indeed.

“The timing of the federal register announcement in juxtaposition with the AGS review is being received by most as the final death sentence for Arecibo,” Kerr says.

Ulvestad says that before any such decision is reached, communities that rely on the observatory will have an opportunity to share their concerns. On June 7, the first of these meetings will take place in Puerto Rico, and a public comment period is open until June 23. After the results of the draft environmental impact statement are released, a 45-day public comment period will follow.

And then? Either the storm will hit or it won’t.

“To be fair to the NSF, AST and AGS are reacting to a very difficult budget situation — no significant increase in several years and none forecast,” Campbell says.

Scanning the Cosmos

View Images Looking down at the dish from above. (Nadia Drake)

Now, Arecibo’s projects include detecting mysterious bursts of radio waves coming from far, far away, testing cosmological models by studying small galaxies in the local universe, and studying those potentially planet-killing asteroids – as well as the moons of distant planets.

“There is much concern, not just in the small bodies community, but in the planetary science community as a whole regarding the future of Arecibo,” says Nancy Chabot of the Johns Hopkins University Applied Physics Laboratory. Chabot chairs NASA’s Small Bodies Assessment Group, which published a report earlier this year urging NASA to continue supporting the observatory, in the name of preserving “the nation’s science and security interests.”

Among astronomers, perceptions are that NSF’s move to decommission Arecibo has been gaining momentum as challenges from new facilities arise. One potential thorn in Arecibo’s side is ALMA, the ultrasensitive array of radio telescopes recently completed in the Chilean Atacama. Some scientists speculate that with continued resources devoted to ALMA, NSF could be looking to share the relative wealth and spend its money on something other than radio. And that might make sense, especially given that China is nearly done constructing a single-dish radio telescope that will be larger than Arecibo. Called the Five-hundred-meter Aperture Spherical Telescope, the behemoth could possibly open its eyes this fall, though real science observations won’t begin right away.

Despite its size, FAST won’t necessarily be more sensitive than Arecibo, and it won’t have a built-in radar, which can be used to give the most accurate orbital information for asteroids which might impact the Earth.

Cornell University’s Jim Cordes points out that newer facilities don’t necessarily have to replace older, high-quality telescopes, especially when those older facilities still provide unique capabilities. They can be complementary, he says, pointing out that scores of similar optical telescopes exist in tandem, such as the two nearly identical Keck telescopes at the summit of Hawaii’s Mauna Kea. “It’s sort of like there’s a disconnect in the way people think about radio telescopes and optical telescopes,” Cordes says.

More importantly, Cordes notes, some experiments actually require multiple extremely sensitive telescopes. One of these, called NANOGrav, uses Arecibo and a telescope at the National Radio Astronomy Observatory in Green Bank, West Virginia to search for gravitational waves. The project does this by observing pulsars, spinning stellar corpses that act as astronomical clocks. As these dense, dead stars rotate, they emit beams of radio waves that can be detected from Earth; gravitational waves, similar to those detected earlier this year by the LIGO collaboration, sweep through and disrupt the signals coming from those spinning clocks in observable ways…as long as a sharp set of eyes is paying attention.

“NANOGrav’s goal is to open a gravitational wave window that parallels what LIGO did so spectacularly,” Cordes says, noting that the two experiments look for waves produced by wildly different cosmic collisions. “The NANOGrav band is as different from the LIGO band as radio waves in the FM band are different from the X-rays used by your dentist. A full understanding of the universe requires instruments that sample all frequencies.”

Losing Arecibo would mean losing the ability to precisely monitor half of NANOGrav’s roughly 50 pulsars. “This will push back detection by a few years, at a time when we are almost there,” says NANOGrav chair Xavier Siemens, of the University of Wisconsin-Milwaukee.

View Images A scientist who shall remain anonymous once described empirically testing whether a motorcycle could be ridden up the catwalk to the telescope’s platform. The answer is yes, which will not come as a surprise to James Bond [note: this is the roof on the catwalk]. (Nadia Drake)

It seems clear that Arecibo won’t go down without a fight, but it’s not exactly clear what form that fight will take. Interestingly, former observatory director Robert Kerr threw one punch by beginning the process for listing Arecibo as a national historic site.

“It was entirely my intention that the National Historic Registry be an impediment to site closure,” he says, adding that “others assisting with that application may have had other motivations, such as enhanced tourist appeal.”

And NASA, which funds the planetary radar experiments at Arecibo, also may have something to say about NSF shutting down the facility. It’s also possible that another institution, or someone with enough spare cash might decide to step in.

“I hope that they do find another institution to contribute to the costs but it will depend on the conditions,” Campbell says. “The alternative is grim for science, for Puerto Rico and, especially given Puerto Rico’s current situation, for the Observatory’s local staff. The staff are an incredible hard working and supportive group.”

Indeed, generations of Puerto Ricans have visited the observatory, in addition to those who have worked, studied, and lived there.

“I grew up in the city of Arecibo, I grew up knowing that in the mountains south of the city great science was being done,” says Pablo Llerandi-Román, a geologist at the University of Puerto Rico, Rio Piedras. For Llerandi, science became more than just a subject in school when he visited the observatory as a student and talked with the researchers on site. “If Arecibo shuts down,” he says, “A major aspect of my arecibeño and Puerto Rican scientist pride would be lost.”

Carlos Estevez Galarza, a student at the University of Puerto Rico, says he hopes Puerto Ricans will one day be as celebrated for their commitment to science as they are for their passions for arts and sports – and he thinks the observatory plays an important role in that.

“The Arecibo Observatory and its staff were the only ones who believed in me, when no one did,” Galarza says. He worked as a student research assistant at the observatory, studying Mars, and has since presented his work at international conferences and submitted his first paper to a science journal.

“The most important thing about my experience at the Arecibo Observatory is that I found my purpose,” he continues. “There are many talented Puerto Rican students who deserve the chance that I had.”

One of those students is still in high school. Now 16, Wilbert Andres Ruperto Hernandez wanted to be an astronaut as a kid – and he wanted to get some hands-on experience in science and engineering. So he enrolled in the Arecibo Observatory Space Academy, which offers high school students the opportunity to design experiments, then collect and analyze data. Now, Hernandez says, he wants to study mechanical engineering or space sciences in college, and has discovered a yearning to understand how the universe works – something that emerged while working with and talking to scientists at the observatory.

“The fact that we have yet to discover and learn more about ourselves, where we live in and all the things that surround us, motivates me the most to investigate and study these fields,” he says. “Being part of Arecibo Observatory and AOSA has been the greatest experience in my life.”