A broken support cable at the Arecibo radio observatory has brought operations to a halt.

An overview of the Arecibo radio telescope. Cables support a triangular platform over the dish, which in turn supports a beam-steering mechanism housed in the dome seen hanging below the platform.

The Arecibo Observatory in Puerto Rico, one of the world's largest radio telescopes, has had its share of rough times, including earthquakes and hurricanes. Just over the past few years, the giant 1,000-foot diameter radio telescope weathered severe budgetary woes and survived a direct hit from the Category 4 Hurricane Maria, for which repairs are still ongoing.

Now Arecibo has suffered damage caused when one of its auxiliary support cables snapped, bringing operations at the observatory to a halt. The damage occurred on Monday, August 10th, at 2:45 a.m. local time, when a three-inch-thick cable snapped and fell to the dish below. No personnel were injured in the incident.

The cable is one of four auxiliary cables per tower that support a triangular platform over the dish. The platform houses the radio dish's beam-steering mechanism, a Gregorian reflector system that focuses incoming radio waves. The telescope is situated at latitude 18.3°N, and its dish is pointed straight at the zenith, but thanks to the beam-steering mechanism near its focus, Arecibo can aim at a swath 20° north-to-south on either side of zenith, expanding its view considerably.

The auxiliary cables and the Gregorian dome were added in an upgrade completed in 1997, and were expected to last 50 years.

Damage to the main dish, as seen from the ground.

The platform is anchored to three towers around the edge of the dish. When the cable snapped, it twisted the platform, and damaged six to eight panels on the suspended dome. The cable fell on the main reflector dish, opening up a 100-foot long gash.

What caused the cable to snap isn’t immediately clear; engineers are still gauging the damage and the time needed for repairs. “We have a team of experts assessing the situation,” says Arecibo Observatory director Francisco Cordova in a recent press release “Our focus is assuring the safety of our staff, protecting the facilities and equipment, and restoring the facility to full operations as soon as possible.”

Looking across the walkway towards the central platform at Arecibo's focus.

The University of Central Florida (UCF) manages the National Science Foundation (NSF) facility in partnership with the Universidad Ana G. Méndez based in San Juan, Puerto Rico and Yang Enterprises Inc. The National Astronomy Ionosphere Center uses the facility, and NASA uses Arecibo's radar for asteroid recon.

Arecibo has faced calamity before. Reduced funding, proposed by the NSF in 2007, would have ultimately shuttered Arecibo, but astronomers, members of the Planetary Society, and others mobilized to protect the facility. Nevertheless, funding issues have continued to plague the observatory.

The dish also sustained damage in 2017 when Hurricane Maria devastated Puerto Rico. That storm damaged the line feed to the main dish, which also took out some of the main dish panels below when it fell.

An Historic Radio Telescope

Built over a natural sink hole, Arecibo began operations in 1963. The Arecibo dish was the largest radio telescope for over half a century, until China’s Five-hundred meter Aperture Spherical Telescope (FAST) dish came online in 2016.

Over the years, Arecibo has proved to be a powerful tool for radio astronomy. The dish has been used to probe Earth’s ionosphere, image and characterize near-Earth asteroids, examine distant pulsars, galaxies, and more. Arecibo has also played a key role in the Search for Extraterrestrial Intelligence (SETI) over the years, collecting data for the SETI@Home project and broadcasting a message to the globular cluster Messier 13 in Hercules in 1974. Arecibo has even turned up on the big screen, in the movies Contact and Golden Eye.

The venerable radio telescope and observatory may be temporarily down for now, but don't count it out just yet.





Image of Peter Wilson

Peter Wilson

August 19, 2020 at 8:13 pm

"...when a three-inch-thick cable snapped and fell to the dish below."

I hate it when that happens!

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