The astronomy community was dealt a significant blow recently when the famous Arecibo Observatory in Puerto Rico collapsed.
The massive platform suspended above the dish collapsed on December 1. The facility had already been scheduled for demolition, after two of the cables holding the structure aloft malfunctioned over the last few months. The National Science Foundation (NSF), which owns Arecibo, determined that there was no way to safely repair the observatory and had planned to demolish it in a controlled manner. But the overhead platform fell on its own, ahead of schedule.
“We are saddened by this situation but thankful that no one was hurt,” said Sethuraman Panchanathan, director of the NSF. “Our focus is now on assessing the damage, finding ways to restore operations at other parts of the observatory, and working to continue supporting the scientific community, and the people of Puerto Rico.”
The observatory consisted of a massive dish—1,000 feet wide and 167 feet deep—embedded in a geological depression known as a karst sinkhole. It is a spherical rather than a parabolic dish, made up of almost 40,000 aluminum panels, each one measuring three by six feet, supported above the sinkhole by steel cables. To the disappointment of James Bond fans, there is no secret underground facility under the dish.
The triangular overhead platform weighed 900 tons and was suspended 450 feet above the dish by 18 cables attached to three reinforced concrete towers. Because it was built into the ground, the dish couldn’t be steered to aim at a particular part of the cosmos—instead, the platform itself was movable: it could be positioned by 26 different motors and could be adjusted with precision down to the millimeter.
Below the main platform was an azimuth arm that featured a carriage house and Gregorian dome that housed two subreflectors. The structure also had an assortment of downward-pointing antenna with highly sensitive radio receivers tuned to specific frequency bands.
In August, an auxiliary cable popped out of its socket and snapped, damaging the platform and tearing a gash in the dish that measured 100 feet long. A team evaluated the damage, pointing to a possible manufacturing defect in the cable, and determined that the remaining cables could bear the load. But in early November, one of the main cables broke—likely increasing the load on the remaining cables. In addition, for several days before the collapse, wires in the remaining cables started snapping and fraying. When the platform finally fell onto the dish, one of its support towers was sheared in half and the tips of the other two broke off as well.
“It was a snowball effect,” said Angel Vazsquez, Arecibo’s director of operations. “There was no way to stop it.... It was too much for the old girl to take.”
The NSF determined that it was too dangerous to repair the observatory; it rejected options such as easing the tension in certain cables or reducing the weight by using helicopters. And since replacing the dish requires authorization from Congress—and would have a price tag of up to $350 million—that didn’t seem like a feasible option either.
The facility withstood more than its fair share of severe weather, including a hurricane in 2017, earthquakes, and the heat and humidity of the Caribbean.
For decades Arecibo had been the largest radio telescope in the world, only surpassed in 2016 by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in Dawodang, China—which was modeled after Arecibo.
The Arecibo Observatory has made significant contributions to our understanding of the universe—helping to identify distant phenomena such as pulsars and quasars, discovering the first-ever exoplanet, mapping Mercury and Venus, and recording radio wave blasts from distant parts of the universe. In 1974, the facility was used to transmit a picture message into space detailing human achievements—in the hope that someone was out there listening.
Arecibo still has functioning equipment that survived the collapse, including two LiDAR facilities and a photometer that study the atmosphere as well as a 12-meter telescope. But the centerpiece of the site is now damaged beyond repair, accelerating its eventual demolition.
While the Arecibo telescope may have come to an end, astronomers are still looking to the stars. Read more about telescope technologies at The Future of NASA’s Space Telescopes.