Second cable failure marks the end for famous Areicbo radio telescope

Yolanda Curtis
November 21, 2020

View of the Arecibo radio telescope primary dish and the spherical reflector, Arecibo Observatory, Puerto Rico in June, 2019.

UCF President Alexander Cartwright said in a news release that the university's team, alongside the NSF, has worked tirelessly to find ways to stabilize the telescope with minimal risk - he said it isn't possible. Scientists worldwide have used the dish along with the 900-ton platform hanging 450 feet above it to track asteroids on a path to Earth, conduct research that led to a Nobel Prize and determine if a planet is potentially habitable.

In August a sub-cable broke, tearing a 30-meter hole in the reflective dish and damaging the dome above it. The NSF authorised the engineering analyses that were the prerequisites for repairs.

A second, main cable that supports the observatory broke on November 6, causing additional damage to the dish and other nearby cables. But on 6 November, another cable broke. Subsequent analysis established that the 76 mm main cable had failed at only 60% of its expected minimum breaking stress during calm weather.

Inspections of other cables revealed breaks and slippages as well. There was also evidence of significant slippage at several sockets holding the remaining auxiliary cables, which were added during a refit in the 1990s that added weight to the instrument platform. As fix crews assessed the new damage, they determined that the structure was unstable and were anxious that the other cables could snap at any time. But they are under threat if the telescope structure collapses. "It is therefore our recommendation to expeditiously plan for decommissioning of the observatory and execute a controlled demolition of the telescope".

Until the assessments from independent engineering companies came in, "our question was not if the observatory should be repaired but how", Gaume said. The other agreed with Thornton Tomasetti that the structure was too risky to work on.

Given the risks to personnel, the NSF made a decision to accept the recommendations of the majority of the engineering entities consulted about the telescope. "While I am disappointed by the loss of investigative capabilities, I believe this process is a necessary step to preserve the research community's ability to use Arecibo Observatory's other assets and hopefully ensure that important work can continue at the facility". Over its life, the radio telescope at Arecibo became part of American, and indeed, wider, popular culture.

The 305-metre radio telescope, made internationally famous by movies such as GoldenEye and Contact, was found to be in danger of a catastrophic failure as its cables may no longer be capable of carrying the loads they were created to support.

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