Annals of Astronomy
The Collapse of Puerto Rico's Iconic Telescope
The uncertain future of the Arecibo Observatory, and the end of an era in space science.
By Daniel Alarcón
For more than half a century, the Arecibo Observatory had the world's largest single-aperture telescope.Illustration by Golden Cosmos
Just before eight in the morning on December 1st of last year, Ada Monzón was at the Guaynabo studios of WAPA, a television station in Puerto Rico, preparing to give a weather update, when she got a text from a friend. Jonathan Friedman, an aeronomer who lives near the Arecibo Observatory, about an hour and a half from San Juan, had sent her a photo, taken from his sister-in-law's back yard, of the brilliant blue Caribbean sky and the green, heavily forested limestone hills. In the picture, a thin cloud of dust hovered just above the tree line; the image was notable not for what it showed but for what was missing. On a normal day—on any day before that one, in fact—a shot from that back yard would have captured Arecibo's nine-hundred-ton radio-telescope platform, with its massive Gregorian dome, floating improbably over the valley, suspended from cables five hundred feet above the ground. Accompanying the photo was Friedman's message, which read, simply, "Se cayó "—"It fell."
Every year since Arecibo's completion, in 1963, hundreds of researchers from around the world had taken turns pointing the radio telescope toward the sky to glean the secrets of the universe. It had played a role in the fields of radio astronomy and atmospheric, climate, and planetary science, as well as in the search for exoplanets and the study of near-Earth asteroids that, were they to collide with our planet, could end life as we know it. There were even biologists working at Arecibo, studying how plant life developed in the dim light beneath the telescope's porous dish.
Monzón, along with thousands of other scientists and radio-astronomy enthusiasts for whom Arecibo held a special meaning, had been on high alert for weeks, ever since two of its cables had failed, in August and in early November. Although the telescope seemed to have survived Hurricane Maria, in 2017, without serious damage, the earthquakes that followed had perhaps weakened components that were already suffering from decades of wear and tear. It was, in many ways, a death foretold. Even so, when the inevitable finally occurred, Monzón was stunned.
Monzón is a presence in Puerto Rico, a much beloved and trusted figure, as meteorologists sometimes are in places where reporting on extreme weather can be a matter of life and death. She'd covered Hurricane Maria and its harrowing aftermath, as well as dozens of lesser but still dangerous storms and the resulting floods or landslides. She'd done a Facebook Live through a magnitude-6.4 earthquake. Still, she told me, the end of Arecibo was somehow harder, more personal. "It was devastating," she said. "One of the most difficult moments of my life." Arecibo, she added, "was a place of unity for everyone who loves science on this island, and all of us who truly love Puerto Rico."
For more than half a century, Arecibo was the world's largest single-aperture telescope, its global reputation built on grand discoveries that matched its size: from the observatory, the presence of ice on the poles of Mercury was first detected, the duration of that planet's rotation was determined, and the surface of Venus was mapped; the first binary pulsar, later used to test Einstein's theory of relativity, was found by astronomers working at Arecibo. (They were awarded a Nobel Prize for the discovery in 1993.)
In 1974, a team led by an astronomer at Cornell University named Frank Drake (which included Carl Sagan) put together the Arecibo Message, a radio transmission that was beamed to a cluster of stars more than twenty-five thousand light-years away. The message was meant to celebrate human technological advancement, and, supposedly, to be decoded and read by extraterrestrials. Not all radio telescopes can both receive and transmit: this was one more way in which Arecibo was special. The message itself—a series of bits and squares containing the numbers one through ten, the atomic numbers of certain elements, and a graphic of a double helix, among other scientific touchstones—was mostly symbolic, to mark the occasion of an upgrade to the telescope's capabilities, but it captured the public imagination nonetheless. In theory, were any alien life-forms to respond, we earthlings could discern their answer at Arecibo.
Each year, more than eighty thousand visitors came to the observatory, including tourists from all over the world and twenty thousand Puerto Rican schoolchildren, who had their first brush with the cosmos there. The 1995 James Bond film "GoldenEye" featured an absurd fight scene that was shot at Arecibo, which culminated in Pierce Brosnan's Bond dropping a scowling villain to his death from the suspended platform; two years later, in the film "Contact," Jodie Foster and Matthew McConaughey shared a kiss beneath a starry sky with the Gregorian dome as a backdrop. "If you had to tell someone about Puerto Rico," Monzón told me, "you'd say, 'We have the largest radio telescope in the world,' and they'd say, 'Oh, sure, Arecibo.' "
"You want me on time, or you want me in a turtleneck?"
Cartoon by Tom Chitty
That December morning at the WAPA studios, Monzón told the production team that she had to go on the air right away, and minutes later she was standing in front of a weather map, her voice cracking: "Friends, with my heart in my hands, I have to inform you that the observatory has collapsed." She bit her lip and shook her head. "We tried to save it however we could. And we knew this was a possibility. . . ." She trailed off, looked down at the phone in her hand, and stammered that the director of the observatory was calling. She answered on air and, for an awkward moment, even wandered off camera. Everything was true, she told her audience when she returned. It was gone.
The construction of a world-class radio telescope in Puerto Rico was, in some ways, an accident of the Cold War. After the Soviet Union launched the Sputnik satellite, in 1957, there was a lot of money in Washington for big ideas that could showcase American power and technology, particularly in space. Enter a Cornell electrical engineer named William Gordon, a veteran of the Second World War in his early forties, who wanted to use radio waves to study the upper atmosphere—something that required a giant transmitter and a massive dish. Nothing on this scale had ever been done. Radio astronomy was still in its early days; Cornell was among the first American universities where it was studied. The Advanced Research Projects Agency, created by President Eisenhower, funded the project, hoping that it would detect any intercontinental ballistic missiles cutting a path across the upper atmosphere.
In order to be useful for planetary study, the telescope had to be situated in the tropics, where the planets pass overhead in their orbits. Cuba, in the midst of revolution, was not an option. Hawaii and the Philippines were too far away. Puerto Rico, which had formalized its colonial relationship with the U.S. less than a decade earlier, emerged as a possibility, facilitated by a Ph.D. candidate from there who was studying at Cornell. The rest, as they say, is history. Gordon, who died in 2010, described the rather arbitrary nature of the site-selection process in a 1978 interview: "Our civil-engineer man looked at the aerial photographs of Puerto Rico and said, 'Here are a dozen possibilities of holes in the ground in roughly the dimensions you need.' And we looked at some and said, 'Well, that's too close to a town or a city or something.' Very, very quickly he reduced it to three, and he and I went down and looked at them and picked one."
The one that they picked was a half-hour drive into the hills from Arecibo, a town of about seventy thousand, with a harbor and a lively central plaza. In the sixties, it was a hub of rum production, home to one of the island's largest cathedrals and three movie theatres. Every year during carnival, people came to Arecibo from all over the island to dance to steel-drum bands. There was a fifty-room hotel on the plaza, where visiting scientists and engineers sometimes stayed, and where the New York Times and the Daily News were delivered every Sunday. Gordon and his team moved to Arecibo in 1960, setting up shop in a small office behind the cathedral. Several other mainland scientists and their families, along with a few Cuban engineers, settled in Radioville, a seaside development a couple of miles west of the center of town—named for a radio station, not for the observatory, which, in any case, was still just an idea.
Size was always a core-value proposition of the observatory at Arecibo. At the time, the largest radio telescope, near Manchester, England, had a diameter of two hundred and fifty feet; Arecibo's telescope would be a thousand feet wide, dwarfing every other such instrument in use. The limestone hills of northern Puerto Rico were dotted with natural sinkholes, which made the excavation and construction simpler, though there was nothing simple about building a spherical dish with the area of approximately eighteen football fields. The curve of the dish had to be precise in order for the radio waves to be gathered within a movable instrument platform. According to the astronomer Don Campbell, who arrived at Arecibo in 1965 and is now working on a history of the facility, the construction of the observatory—which was built at a cost of around nine million dollars, the equivalent of more than seventy million today—was a tremendous achievement.
The original walkway to the suspended platform had wooden slats. There was no phone communication from the observatory to the city, though there was a radio link to a phone that rang on the fourth floor of the Space Sciences Building at Cornell. Back then, the trip from San Juan to the observatory might take two or three hours, longer during the harvest season, when trucks piled high with sugarcane clogged the narrow roads. Joanna Rankin, a radio astronomer at the University of Vermont, who made her first observation at Arecibo in 1969, told me that the terrain at the site was so steep and unforgiving she found it miraculous that the place had even been built. "Going up there at night was like being on an island in the sky," she said. "So vast and so delicate." The facility attracted an adventurous sort of personality in those early days, Campbell said. Still, it was good living: the scientists worked hard all week and went to the beach every Sunday. The Arecibo Country Club, which had no golf course and whose swimming pool was often drained of water, nonetheless hosted great parties, to which the scientists were often invited. And, of course, the chance to work on a telescope of that magnitude was unique.
Planetary and atmospheric researchers used Arecibo to transmit a radio signal toward a target—a planet, an asteroid, the ionosphere—and deduced information from the echoes that came back. Radio astronomers, on the other hand, mostly listened to naturally occurring radio waves that originated in space—what was once known as "cosmic noise." Because radio astronomy doesn't require darkness, Arecibo operated at all hours of the day and night, and several of the scientists I spoke to described a tight-knit community, with colleagues working across disciplines, delighting in one another's discoveries. When word came that Joseph Taylor and Russell Hulse had won the Nobel Prize, in 1993, it was as if all the scientists at Arecibo had won it. Those who heard the news while having breakfast in the cafeteria danced joyfully around the table. Taylor later had a replica of the prize made for the observatory's visitors' center.
The instruments and equipment at Arecibo were in a constant state of reinvention. In 1974, the wire mesh that originally formed the spherical surface of the dish was swapped for roughly forty thousand perforated-aluminum panels, which made it possible to observe at higher frequencies. The most striking upgrade came in the nineties, with the twenty-five-million-dollar construction of a Gregorian dome, to house more sensitive instrumentation, which added an extra three hundred tons of weight to the platform. According to Campbell, Gordon, who had retired by then, visited the site and joked that the addition "destroyed the symmetry of my telescope."
The problems began for Arecibo in the mid-aughts, when the National Science Foundation, which owned the site and supported it with about twelve million dollars a year, convened a panel of astronomers to evaluate the foundation's holdings. With the N.S.F. facing flat budget allocations, and with several large investments in new telescopes under way, the panel recommended a multimillion-dollar cut to the Arecibo astronomy budget, to be implemented over several years. The report was stark and final: if partners couldn't be found to help cover the cost of maintaining the site by 2011, Arecibo should be closed.
According to Daniel Altschuler, who was then the observatory's director of operations, the report had a catastrophic impact on morale. But Congress provided a lifeline when it mandated that NASA track at least ninety per cent of near-Earth objects larger than four hundred and fifty feet—the kind, in other words, that could wipe out entire cities. As it happened, Arecibo's powerful transmitter could beam radio waves at asteroids and measure their size, the quality of their surface, their speed, their orbit, and their rotation in astonishing detail. This added a few million dollars to the yearly budget—a stay of execution, more or less, which eased the pressure without providing a long-term solution. Scott Ransom, a staff astronomer at the National Radio Astronomy Observatory, in Charlottesville, Virginia, made observations from Arecibo for twenty years. He told me that there was always a sense that the facility was living on borrowed time. "The next hurricane, the next earthquake, the next downturn in the economy, the next political turn was going to be the end for Arecibo," he said.
Bob Kerr, who became the director four years after Altschuler left, said that the observatory had somehow become "the poster child for so-called life-cycle planning"—the notion that limited funds require decision-makers to decommission older facilities as new ones are developed. Even now, Kerr finds this attitude mystifying. Not only were the scientists at Arecibo still producing cutting-edge research but the observatory played a significant role in fulfilling many of the N.S.F.'s stated goals, including democratizing access and inspiring young people, particularly Puerto Rican and other Latino students, to enter the sciences. "These are things that you would have thought N.S.F. would have held as a jewel in the crown," Kerr said. "I've never been able to understand why N.S.F. walked away from that accomplishment." In 2015, he resigned. "Many staff members feared they would have to be the ones to turn off the lights," he told me.
In 2018, less than a year after Hurricane Maria, a partnership led by the University of Central Florida took over management of the observatory. Ray Lugo, the director of U.C.F.'s Florida Space Institute, who was appointed after a long career at NASA, told me that, when Cornell oversaw the observatory, contributions from the N.S.F. ran to tens of millions of dollars a year. U.C.F. has enjoyed no such largesse. By 2023, the last year of its contract, N.S.F. contributions are slated to be reduced to just two million dollars. "They're looking for a graceful exit," Lugo said. U.C.F. proposed that the N.S.F. pass the title and ownership of the site to the State of Florida, which would mean that a significant part of the fight for dollars to support the observatory would take place in Tallahassee, not Washington. But the move stalled, according to Lugo, because of opposition from José E. Serrano, a congressman representing New York, who has since retired. (Serrano, who was born in Puerto Rico, saw support of Arecibo as a federal commitment to the people there. "I didn't want to let the N.S.F. wash their hands of it," he said.)
"No, I'm not interested in your new hygiene protocol."
Cartoon by P. C. Vey
Meanwhile, the damage from Hurricane Maria was assessed, and the consensus was that the telescope had been spared any serious impact—something of a miracle, considering the power of the storm. It's less clear what the consequences of the thousands of earthquakes that shook the island in early 2020 may have been. In any case, maintenance and repair on the instrument, given its size and complexity, had always been somewhat ad hoc. "It's not as if replacement parts can be taken off the shelf," Luisa Fernanda Zambrano, a Ph.D. candidate who has worked at Arecibo for seven years, told me. "If something broke, repairs were always a little bit MacGyver."
The first cable came loose on August 10th, tearing a hundred-foot gash in the dish and damaging about two hundred and fifty of its panels. It was concerning, but did not, at the time, seem to represent an existential threat to the observatory itself. The N.S.F. authorized the purchase of replacement parts. Then, on November 6th, while engineers were still studying how repairs could be made, a second cable broke. At that point, there was no way back. On November 19th, the N.S.F. declared that Arecibo's telescope would be decommissioned, pending an analysis of the safest way to disassemble it. That question became moot less than two weeks later, when the remaining cables gave way. The observatory, the most iconic symbol of U.S. investment on the island for nearly six decades, was gone. All that was left, in Lugo's words, was "a bunch of aluminum panels sitting at the bottom of a sinkhole."
A few days after the collapse, the N.S.F. released a video of the moment the telescope fell, shot from a drone flying just above the Gregorian dome. The soundless video shows the cables beginning to unravel, first one, then another, then several strands snapping at once, before the camera turns, gazing suddenly down at the ruined dish. Another video, taken from below, near the base of one of the towers from which the dome was suspended, shows the scene with sound, an ominous, heaving rumble before the cables give and the platform swings behind the trees and offscreen. The tops of the towers snap like matchsticks.
Online, videos of the collapse were sometimes posted with a trigger warning. Chris Salter, an astronomer who worked at Arecibo for twenty-six years, told me that he hadn't been able to bring himself to watch them yet. "It's like losing a family member," he said. On social media, hundreds of Puerto Rican scientists and students posted tributes to the observatory, under the hashtags #WhatAreciboMeansToMe and #SaveTheAO. To scroll through them was to be struck again and again by the staggering scale of the loss. According to scientists at Arecibo, data collected there has fuelled thirty-five hundred scientific publications and nearly four hundred master's or Ph.D. theses. More than twenty asteroids were studied from the observatory and named after Arecibo scientists and technicians. Abel Méndez, an astronomer at the University of Puerto Rico at Arecibo, told me that the very presence of the observatory had helped him overcome the impostor syndrome that might otherwise have plagued him, as a working-class kid from a public school who dreamed of entering the sciences. He'd first seen the telescope as an eleven-year-old boy. There was no visitors' center then, so he had called from a pay phone across the street from his school and asked if he could tour the observatory. "They took me beneath the dish," he said. "To have a place like that here, in Puerto Rico, it gave me a sense of confidence."
The collapse came at a particularly fraught moment for Arecibo. Every ten years, scientists from the various branches of astronomy produce a document, a kind of road map for the coming decade of research, setting priorities for new instruments and the most promising fields of investigation—all of which is a precursor to the allocation of N.S.F. funding. Before the collapse, the team at U.C.F. and collaborators had written more than twenty-five white papers arguing for the continued value of the observatory's work. They were, until December, cautiously optimistic, but unfortunately the decadal committee's review was nearly complete when the telescope fell. There was no indication that it would be modified at such a late date to take what had happened at Arecibo into account.
When the second cable broke, a group of astronomers from around the world began holding daily vigils on Zoom. After the collapse, the focus of those meetings widened to include plans for rebuilding. There was a sense of urgency, a desire to take advantage of the public outpouring of grief. Some of the scientists, led by Arecibo's head of radio astronomy, D. Anish Roshi, met through December and January, and in early February released another white paper, with a proposed design for what they called the Next Generation Arecibo Telescope. The telescope, which would cost an estimated four hundred and fifty million dollars to build, would provide five times more sky coverage than the fallen instrument, with more than double the sensitivity in receiving radio signals and four times the transmitting power. Some two thousand scientists and enthusiasts in more than sixty countries endorsed the white paper. In a statement to me, an N.S.F. spokesperson wrote that the foundation had received the paper and was still "collecting such input." In a report released in early March, the N.S.F. said that it was planning a community workshop this summer to encourage the submission of proposals for the future of the observatory.
Many Puerto Ricans, though, fear that Arecibo will be yet another illustration of the abandonment and neglect that have colored many aspects of life on the island. It's been decades since Puerto Rico was the prosperous tropical outpost of American capitalism, used as a contrast and a cudgel against socialist Cuba. The brightest years of the island's economy corresponded with the golden age of Arecibo, when the observatory was buzzing and the science was at its most revolutionary. The tax exemptions that fuelled Puerto Rico's economy were phased out the year before the N.S.F. first threatened to shut down the observatory. The island has been in recession for the majority of the past fifteen years, while its debt has ballooned to more than seventy-two billion dollars—a figure so preposterous that, in 2015, Alejandro García Padilla, Puerto Rico's governor at the time, announced that it was simply unpayable. Even before Hurricane Maria, the population had shrunk by more than ten per cent from its peak, in the mid-two-thousands; after the storm, an estimated hundred and thirty thousand people moved to the mainland. And the earth continues to shake: right now, the island is experiencing hundreds of tremors every month. "We've been through a lot," Monzón told me. "There are people who don't like the word 'resilience,' but that's really what defines us." Nonetheless, the fall of Arecibo was a painful setback.
When I spoke to Lugo in mid-February, he told me that workers were preparing to clear away the debris from the shattered Gregorian dome, cutting it free from the limestone into which it had embedded itself when it fell. Some aspects of the grim cleanup, which was projected to cost between thirty million and fifty million dollars, were already under way, and the hundred or so Puerto Rican staff members on site were struggling. On more than one occasion, Lugo told me, he'd turned a corner and come across an employee, alone, overcome with emotion. Lugo, who is of Puerto Rican descent, understood what they were going through, because he was going through it, too. Zambrano was assigned to a team tasked with salvaging parts from the debris, but for weeks she avoided looking directly at the damage. When she finally did so, in early February, she wept. Among the ruins, her team found two seven-foot klystrons—specialized vacuum tubes that amplify radio frequencies—that had somehow survived the crash nearly intact. They had been installed shortly before the first cable broke and had never been used. Now she wondered if they might be saved, not to be used as intended but to be part of a museum exhibit about what Arecibo had once been. ♦
An earlier version of this story misstated the profession of William Gordon.
Published in the print edition of the April 5, 2021, issue, with the headline "The Collapse at Arecibo."
Daniel Alarcón is a contributing writer at The New Yorker and the executive producer of "Radio Ambulante," a Spanish-language podcast. He teaches at the Graduate School of Journalism at Columbia University.
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