The damaged 305-meter radio telescope at Arecibo Observatory in Puerto Rico will be decommissioned due to safety concerns, the National Science Foundation (NSF) announced on November 19. The iconic dish has served as a backdrop for several science fiction movies. The Arecibo Observatory Amateur Radio Club, KP4AO, is headquartered at the research facility, and several radio amateurs are employed there.

“Following a review of engineering assessments that found damage to the Arecibo Observatory cannot be stabilized without risk to construction workers and staff at the facility, the US National Science Foundation will begin plans to decommission the 305-meter telescope, which for 57 years has served as a world-class resource for radio astronomy, planetary, solar system, and geospace research,” the NSF said. “The decision comes after NSF evaluated multiple assessments by independent engineering companies that found the telescope structure is in danger of a catastrophic failure, and its cables may no longer be capable of carrying the loads they were designed to support.”

NSF said several assessments suggested that any attempts at repairs could put workers in potentially life-threatening danger, and even if repairs were possible, engineers found that “the structure would likely present long-term stability issues,” NSF said.

NSF Director Sethuraman Panchanathan expressed regret about what he called “a profound change,” and said the observatory will explore ways to assist the scientific community and maintain its strong relationship with the people of Puerto Rico.

Engineers have been examining the monster dish since August, when one of its support cables let go. NSF authorized the University of Central Florida, which manages Arecibo, to take what it called “all reasonable steps and use available funds to address the situation while ensuring safety remained the highest priority.”

Engineers had designed, and were ready to implement, emergency structural stabilization of the auxiliary cable system, but while arranging delivery of two replacement cables and two temporary cables, a main cable broke on the same tower on November 6. Based on the stresses borne by the second broken cable, engineers concluded that the remaining cables were likely weaker than originally projected. The cables, connected to three towers, suspend a 900-ton instrument platform that hangs 450 feet above the dish.

“Until these assessments came in, our question was not if the observatory should be repaired but how,” said Ralph Gaume, director of NSF’s Division of Astronomical Sciences. “But in the end, a preponderance of data showed that we simply could not do this safely. And that is a line we cannot cross.”

The decommissioning plan focuses only on the 305-meter telescope and is intended to safely preserve other parts of the observatory that could be damaged or destroyed in the event of an unplanned, catastrophic collapse, NSF said. “The plan aims to retain as much as possible of the remaining infrastructure of Arecibo Observatory, so that it remains available for future research and educational missions.” — The National Science Foundation