The Arecibo Observatory in Puerto Rico is in danger of collapsing

One of the most venerable radio telescopes in the world is on the brink of catastrophe, triggering a frenzied race by engineers at the Arecibo Observatory in Puerto Rico to save it after breaking two critical cables supporting a 900-ton equipment platform.

The platform, held aloft on an enormous dish by cables tied to the towers, must be stabilized quickly, otherwise it could crash to the ground and destroy the telescope. With the loss of these two cables, the remaining cables are more stressed and it is unclear whether the rescue efforts will be successful.

“For me, it’s probably fifty-fifty,” says former observatory director Michael Nolan, now at the University of Arizona. “They are doing what they can do. I’m still very worried they can’t do enough. If we’re worried about it falling, no one should go up there or be there when it happens. “

Suspended in three towers, the telescope platform hovers about 500 feet above the thousand-foot-wide dish. In August, an auxiliary cable slipped from the socket and plunged into the dish, carving a 30-meter-long gash in its reflective panels. Before the teams could repair that cable, another one attached to the same tower broke on November 6. This second broken cable is one of the four main cables connecting that tower to the platform.

“I wasn’t that worried when the first cable failed because I was confident it would take a few months to repair,” says Abel Méndez, an astronomer at the University of Puerto Rico at Arecibo who often observes with a telescope. But Méndez says he was stunned when the second cable failed. “Now I’m worried.”

Arecibo has played a crucial role in identifying planets beyond our solar system, in researching extraterrestrial civilizations, and in studying asteroids and other worlds closer to home. Today, scientists use the telescope to study powerful bursts of energy called fast radio bursts and to spy on ripples in the fabric of space-time produced by the collision of galaxies.

Each of the observatory towers has four main cables, but only two are needed to keep the platform aloft, provided they are in good condition. Tower four (named because it is at the four o’clock position if noon is north) is now reduced to just three primaries. If another of these cables fails, it’s unclear whether two outdated cables will be able to support the platform.

“It’s definitely a bad situation,” says Frank Drake, a former Arecibo director (and my father). “When you have cables breaking like this, a chain reaction could occur at any moment with multiple cables breaking and the whole thing falling.”

It would be a blow to the ongoing scientific observations and to Puerto Rico, where the observatory is a source of pride, providing jobs, attracting tourists and sharing resources with surrounding communities, especially during emergencies like Hurricane Maria.

Several engineering firms and the U.S. Army Corps of Engineers are in the field to assess the compromised platform, while daily drone inspections provide cable updates. Teams are exploring ways to stabilize the structure, including removing some weight from the platform using helicopters, removing tension from the system by lowering the platform, and reconnecting the dropped auxiliary cable, which is still largely intact after slipping. from its grasp.

“We’ll probably know soon enough if they can invent a patch, take some tension off, eliminate the immediate problem so we can fix the big problem,” Nolan says.

In the 1960s, engineers built the giant Arecibo radio dish in one of Puerto Rico’s natural sinkholes. An elevated triangular platform helps point the telescope to different parts of the cosmos. That platform is filled with receivers, line feeds, and a complex reflector system that precisely focuses the radio waves, and this is where James Bond fought Alec Trevelyan in 1995. Golden eye.

While it may seem small compared to the antenna, the suspended structure is really massive – a small house could easily fit inside the dome housing the reflector system.

The platform is supported by 18 thick steel cables tied to three concrete towers, the tallest of which measures 365 feet. In addition to the four primary cables on each tower, two auxiliaries per tower were installed in the 1990s to help stabilize the structure and bear additional weight.

Observatory staff regularly inspect the towers, cables and platform, looking for any signs of weakening or corrosion caused by the brackish and tropical air.

“There’s nothing worse, from a corrosion standpoint, than salt spray,” says Dennis Egan, an engineer at the Green Bank Observatory in West Virginia. “It’s better to be underwater.”

Those inspections revealed some evidence of broken wires in the cables, a problem Nolan suspects may have been compounded by Hurricane Maria and a recent swarm of sizable earthquakes. But they found no indication of widespread weakening or impending bankruptcy. In a question and answer session posted on Facebook, Arecibo director Francisco Córdova said the rupture was unexpected and indicative of structural degradation.

The observatory “is 50 years old and there has never been a situation where suddenly a whole bunch of different wires broke,” says Drake, who famously sent a message into space from the observatory in 1974. “I don’t want to be. about that thing now. There’s no escape. You’re just stuck. “

If tower four fails, the platform could crash into the plate or make a commuter swing into a nearby cliff. Without the weight of the platform holding the towers in balance, it’s possible that all three could fall into the surrounding jungle.

If the engineers can stabilize the structure, they can repair or replace some obsolete cables. Two new cables are already in order, Córdova said on Facebook, which are expected to arrive at the observatory in December.

But to replace the cables, workers will have to step onto the platform. “They have to do something to verify that the existing cables are correct and undamaged, in a way that doesn’t endanger the people on the facility,” Drake says.

The Arecibo Observatory has faced a number of challenges in recent years, including threats from the National Science Foundation to wrest funds. But scientists and surrounding communities rallied and the University of Central Florida stepped in to run the besieged observatory.

Now, many are wondering if NSF will help Arecibo overcome this emergency. According to Córdova’s social media post, NSF is looking into a request for $ 12.5 million in repair funding.

“NSF is in communication with Arecibo. We are monitoring the situation and considering all possible options to speed up the stabilization of the facility, “the agency said in a statement.” Our top priority is the health and safety of Arecibo personnel. “

Despite its current problems, the observatory has had a long and legendary history, occupying a place of pride among scientists and Puerto Ricans.

“It took root in our culture in Puerto Rico, in the fabric of our daily life,” says Edgard Rivera-Valentín of the Lunar and Planetary Institute, whose grandfather helped build the telescope. “I definitely have this memory of being shocked by this huge tool, right here, and knowing that people in my city were doing all these really interesting things,” says Rivera-Valentín. “I work in science because I grew up near the observatory.”

Arecibo’s discoveries include the 1974 detection of a pair of swirling pulsars emitting gravitational waves – which earned the Nobel Prize in Physics in 1993 – and the first confirmed planets sighted orbiting a star other than the sun in 1992. Scientists at Arecibo they also worked out Mercury’s rotational speed, spotted a repeated fast radio burst, and conducted extensive research for communicative extraterrestrial civilizations, an effort popularized by Carl Sagan’s novel Contact which was later made into a movie of the same name.

In addition to observing the skies and collecting radio waves, Arecibo is also an extremely powerful radar. Scientists use this ability to characterize asteroids as they pass through Earth’s orbit, calculating their positions with pinpoint accuracy to figure out how to avoid future collisions. And in 1974, Dad used it to send an interstellar message to a cluster of stars called the Great Cluster in the constellation of Hercules. In it, he encoded information about humans, the Earth, the solar system, and Arecibo, and relayed it during a celebration of telescope updates.

“He does atmospheric science, he does solar system science, he does astronomy, he does astrophysics,” says Rivera-Valentín. “It is important for science and for the whole world.”