Arecibo radio telescope collapses before demolition> ENGINEERING.com

The 900-ton platform suspended above the iconic observatory collapsed. (Image courtesy of media.ambito.com.)

The astronomy community took a significant hit recently when the famous Arecibo Observatory in Puerto Rico collapsed.

The huge platform suspended above the plate collapsed on December 1. The facility had already been scheduled for demolition, after two of the cables that held the structure upright malfunctioned in recent 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 aerial platform fell on its own, earlier than expected.

“We are saddened by this situation, but we appreciate that no one was injured,” said Sethuraman Panchanathan, director of the NSF. “Our focus now is to assess the damage, find ways to restore operations in other parts of the observatory, and work to continue supporting the scientific community and the people of Puerto Rico.”

https://www.youtube.com/watch?v=b3AASKr_iHcImages from the National Science Foundation of the collapse of the observatory.

The observatory consisted of a huge 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 parabolic dish, made up of nearly 40,000 aluminum panels, each three by six feet, held over the sump by steel cables. To the disappointment of James Bond fans, there is no secret underground facility under the plate.

The triangular aerial platform weighed 900 tons and was suspended 450 feet above the plate by 18 cables connected to three reinforced concrete towers. Because it was built into the ground, the dish could not be directed to point to a particular part of the cosmos; Instead, the platform itself was mobile – it could be positioned by 26 different motors and it could be fine-tuned down to the millimeter.

Beneath the main platform was an azimuth arm that featured a carriage house and a Gregorian dome that housed two sub-reflectors. The structure also had a variety of downward-pointing antennas with high-sensitivity radio receivers tuned to specific frequency bands.

This is what Arecibo looked like when it was in working order.

This is what Arecibo looked like when it was in working condition. (Image courtesy of Nature).

In August, an auxiliary cord came out of its socket and broke, damaging the platform and opening a gash in the platter that was 100 feet long. A team evaluated the damage, pointing to a possible manufacturing defect in the cable, and determined that the remaining cables could carry the load. But in early November, one of the main cables broke, probably increasing the load on the remaining cables. In addition, for several days before the collapse, the cables of the remaining cables began to break and fray. When the platform finally fell onto the plate, one of its support towers snapped in half and the tips of the other two also broke.

“It was a snowball effect,” said Ángel Vázsquez, Arecibo’s director of operations. “There was no way to stop it … It was too much for the old woman to take.”

The NSF determined that it was too dangerous to repair the observatory; He rejected options such as relieving stress on certain cables or reducing weight through the use of helicopters. And since replacing the plate requires congressional authorization, and would cost up to $ 350 million, that didn’t seem like a feasible option either.

The facility withstood more than its fair share in adverse weather conditions, including a 2017 hurricane, earthquakes, and the heat and humidity of the Caribbean.

For decades, Arecibo had been the world’s largest radio telescope, second only to the 500-meter aperture spherical radio telescope (FAST) in Dawodang, China in 2016, which was inspired by 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 exoplanet, mapping Mercury and Venus, and recording radio wave bursts from distant parts of the universe. In 1974, the installation was used to broadcast an imagery message to space detailing human achievements, in the hope that someone was listening.

Arecibo still has equipment in operation 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, hastening its eventual demolition.

While the Arecibo telescope may have come to an end, astronomers are still looking at the stars. Read more about telescope technologies at The future of NASA space telescopes.

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