On 10 August a cable popped out of its socket and whipped down to gouge a huge hole in the 305-meter-diameter Arecibo radio telescope dish. Studies were launched to understand why the cable failed, and a replacement cable was due to arrive in December. Then, on 6 November, another cable snapped, precipitating an about-face: Arecibo’s owner, NSF, announced on 19 November that the telescope in Puerto Rico will be decommissioned.
That decision closes the 57-year-old radio telescope, long the world’s largest eye on the sky. (China’s Five-Hundred-Meter Aperture Spherical Telescope began full operations this past January; its effective aperture is the same as Arecibo’s at zenith, but it samples a narrower range of radio frequencies and does not include a radar transmitter.) Among the major discoveries at Arecibo were the first binary pulsar, the first exoplanet, and an ionized helium layer in the upper ionosphere. The telescope was part of the NANOGrav project’s search for gravitational waves using pulsars (see Physics Today, July 2017, page 26). And it featured in the films Contact and GoldenEye.
The Arecibo Observatory was also a key part of NASA’s congressionally mandated planetary defense program to monitor near-Earth objects. But in a 19 November statement, NASA said that those search efforts “are not impacted by the planned decommissioning of Arecibo’s 305m radio telescope.”
The reversal from fix-up to finish-off was a matter of safety, Ralph Gaume, director of NSF’s division of astronomical sciences, said in a telephone news conference. Several engineering firms had evaluated the site and warned of an “uncontrolled catastrophic collapse” if left untouched, he said. The decision to decommission is based entirely on “safety and structural stability,” emphasized Ashley Zauderer, the NSF program director for the Arecibo Observatory. She noted that the agency had recently funded a new ultrawide band receiver for the telescope. Now it has given the green light to plan a controlled deconstruction of the dish.
The cables support a 900-ton platform and dome housing instrumentation that hovers 150 meters above the dish. The causes of the failures are unknown. The first to fail was an auxiliary cable that dated to an upgrade in the 1990s. The second was a main cable from the original telescope construction in 1963; it snapped on a calm day, bearing a load of 647 000 pounds, well below what it was rated for. According to NSF and the University of Central Florida (UCF), the lead contractor for the observatory, maintenance and inspections were current.
Robert Kerr, Arecibo director in 2007–08 and 2011–15, says he “takes the engineers and the NSF at their word that the best option is to decommission the telescope.” He attributes the failures to natural aging and a confluence of external events—a magnitude 6.4 earthquake in 2014, Hurricane Maria in 2017, and a series of temblors in late 2019. In addition, the 1995 upgrade increased the platform weight. The telescope was, he says, “as well maintained as a steel platform in the tropics can be.”
But John Mathews, an emeritus professor at the Pennsylvania State University who visited and used Arecibo regularly from 1969 through 2019, says that “deferred maintenance has been a problem for decades, and it’s only gotten worse.” He points to visible corrosion of dish components and sagging smaller cables. Those are external features, he admits, “but many of us suspected that the structure was compromised.” He adds that “the ship was sinking, and the people who could get jobs elsewhere wisely did so” after the transition to the current UCF-led management team in 2018. In conversations with Physics Today, many Arecibo users and employees suggested that the morale among employees was as frayed as the cables that broke.
Some people interviewed for this story requested anonymity for fear of retaliation. Many Arecibo employees say there has been a lot of discontent in the past couple of years. “The family atmosphere is totally gone,” says one. The people working there have different benefits, depending on which of three entities in the management consortium employs them. Some people took pay cuts, he says, and some don’t have retirement packages.
A scientist who left recently says that some observing time was awarded based on friendships rather than merit. “I was a loud voice against stupid decisions and the toxic environment that my colleagues and I faced since UCF took over managing the observatory,” she says. “Finding friends and colleagues crying on the stairs became routine.”
Kerr notes that Arecibo has been headed toward decommissioning since the 2005 NSF “senior review” of astronomy facilities, in which the agency was looking to free up funds for the Atacama Large Millimeter Array and other new endeavors (see Physics Today, October 2005, page 30). “It’s been a battle between the communities who love Arecibo and NSF,” says Kerr.
Since the senior review, management has changed twice—first moving in 2011 from longtime manager Cornell University to a consortium led by SRI International, and then in 2018 to the current management team. The managers were charged with finding new sources of funding as NSF divested, reducing its 2018 contribution of roughly $8 million to the observatory’s annual budget of $12 million to about $2 million in 2023.
Arecibo was a world-class observatory. It was also an economic driver and an educational hub for Puerto Rico. Nearly every schoolchild on the island visits the site. And the observatory is credited with inspiring many Puerto Ricans to go into STEM fields; the University of Puerto Rico at Mayagüez graduates the most Hispanic engineers and the second largest number of female engineers of any US university, according to a Government of Puerto Rico website. Many members of the observatory staff have worked at Arecibo for decades, notes Kerr. The closure will have a huge impact on the community. Some 100–120 people are employed at the observatory. “I think of the guys who work on the platform,” he says. “They do it all—adjust and hoist instruments, maintain the platform. They make about $45 000 a year, astonishingly little given the risk involved in their job.”
In the decommissioning process, Gaume stressed that the visitors’ center, the lidar facility, and a set of instruments that measure winds, temperatures, and structures in the ionosphere at a separate site about 160 km east on the island of Culebra will be preserved. But the visitors’ center is likely to be less of a draw if people look at a sinkhole rather than a telescope dish. And, Kerr says, those facilities are “in the noise” in terms of the money and scientific productivity.
