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NSF begins planning for decommissioning of Arecibo Observatory’s 305-meter telescope for safety reasons | NSF

News release 20-010

NSF begins planning for decommissioning of Arecibo Observatory’s 305-meter telescope for safety reasons

The 900-ton instrument platform in the 305-meter telescope of the Arecibo Observatory, hanging 405 feet above the telescope's plate.

The 305-meter telescope of the Arecibo Observatory in November 2020.

November 19, 2020

Following a review of engineering assessments that found that damage to the Arecibo Observatory could not be stabilized without risk to construction workers at the facility, the U.S. National Science Foundation will begin plans to decommission the 305-meter telescope, which in for 57 years it has served as a world-class resource for radio astronomy, planetary, solar and geospatial research.

The decision comes after NSF evaluated a number of assessments by independent engineering companies, which found that the telescope̵

7;s design was in danger of catastrophic damage and its cables may no longer be able to withstand the loads for which they were intended. In addition, several assessments indicate that any attempt at repair could expose workers to a potentially life-threatening situation. Even in the case of forward repairs, engineers have found that the structure is likely to pose long-term stability problems.

“NSF prioritizes the safety of employees, visitors and visitors to the Arecibo Observatory, which makes this decision necessary, albeit unfortunate,” said NSF Director Sethuraman Panchanathan. “For almost six decades, the Arecibo Observatory has served as a beacon for breakthrough science and what a partnership with the community might look like. Although this is a profound change, we will look for ways to support the scientific community and maintain this strong relationship with the people of Puerto Rico. “

Engineers have been exploring the Arecibo Observatory’s 305-meter telescope since August, when one of its supporting cables disconnected. NSF has mandated the University of Central Florida, which runs Arecibo, to take all reasonable steps and use available resources to deal with the situation, while security remains the highest priority. UCF acted quickly and the assessment process followed the expected schedule, taking into account the age of the facility, the complexity of the design and the potential risk to workers.

The engineering teams have designed and were ready to implement emergency structural stabilization of the auxiliary cable system. While the observatory was arranging the supply of two additional auxiliary cables, as well as two temporary cables, a main cable broke on the same tower on November 6. Based on the stresses of the second broken cable – which had to be within the ability to function without breaking – the engineers came to the conclusion that the other cables were probably weaker than originally intended.

“Management at the Arecibo Observatory and UCF have done a commendable job of dealing with this situation, acting quickly and pursuing all possible options to save this incredible instrument,” said Ralph Gom, director of the NSF’s Department of Astronomical Sciences. “Until these assessments came in, our question was not whether the observatory needed to be repaired, but how. But in the end, the predominance of the data showed that we just couldn’t do it safely. And that’s a limit we can’t cross. . “

The scope of the NSF decommissioning plan will focus only on the 305-meter telescope and is designed to safely preserve other parts of the observatory that could be damaged or destroyed in the event of an unplanned, catastrophic collapse. The plan aims to preserve as much of the Arecibo Observatory’s infrastructure as possible so that it remains available for future research and educational missions.

The decommissioning process includes the development of a technical implementation plan and ensuring compliance with a number of legal, environmental, safety and cultural requirements in the coming weeks. The NSF has authorized a high-resolution photographic study using unmanned aerial vehicles and is considering options for forensic assessment of the broken cable – if such an action can be done safely – to see if any new evidence could inform current plans. This work has already started and will continue throughout the decommissioning planning. Equipment and other materials will be temporarily relocated to buildings outside the danger zone. When all the necessary preparations have been made, the telescope will be subjected to controlled disassembly.

Following the decommissioning of the telescope, NSF will intend to restore asset operations such as the Arecibo LIDAR Observatory, a valuable geospatial research tool, as well as at the Culebra Visitor Center and off-site, which analyzes cloud and precipitation data. NSF will also seek to explore opportunities to expand the educational capabilities of the training center. The safety precautions due to the COVID-19 pandemic will remain in place as appropriate.

Some Arecibo operations, including analysis and cataloging of archived data collected by the telescope, will continue. UCF has provided enhanced cloud storage and analytics capabilities in 2019 through an agreement with Microsoft, and the observatory is working to migrate data on the spot to servers outside the affected area.

Areas of the observatory that could be affected by an uncontrolled collapse were evacuated from a cable outage in November and will remain closed to unauthorized personnel during decommissioning. NSF and UCF will work to minimize risk in the area in the event of an unexpected collapse. NSF gave priority to a fast, thorough process with the intention of avoiding such an event.

The NSF recognizes the cultural and economic importance of the Arecibo Observatory for Puerto Rico and how the telescope serves as an inspiration for Puerto Ricans considering education and work at STEM. The NSF aims to work with the Puerto Rican government and other stakeholders and partners to explore the possibility of using resources from the Arecibo Observatory for educational purposes.

“Throughout its life, the Arecibo Observatory has helped transform our understanding of the ionosphere by showing us how density, composition and other factors interact to shape this critical region where the Earth’s atmosphere meets space,” said Michael Wiltberger, chief executive. of the NSF Geospatial Section. “While I am disappointed with the loss of investigative capacity, I believe that this process is a necessary step to preserve the ability of the research community to use the remaining assets of the Arecibo Observatory and to hope that important work will continue at the facility.”

Engineering resume

The Arecibo Observatory Telescope consists of a radio with a width of 1,000 feet (305 meters) in diameter with a 900-ton instrument platform suspended from 450 feet above. The platform is suspended by cables connected to three towers.

On August 10, 2020, an auxiliary cable failed, slipped out of its socket in one of the towers, and left a 100-foot slot in the vessel below. The NSF has mandated the Arecibo Observatory to take all reasonable steps and use the available millions of dollars to provide the analysis and equipment needed to deal with the situation. Engineers were working to determine how to repair the damage and determine the integrity of the structure when a main cable connected to the same tower broke on November 6.

The second broken cable was unexpected – engineering assessments after the failure of the auxiliary cable showed that the structure is stable and the planning process for the restoration of the telescope in operation is underway. Subsequently, the engineers found that this 3-inch main cable snapped to about 60% of the minimum breaking strength in quiet weather, which increased the possibility of other cables being weaker than expected.

Inspections of the remaining cables revealed new wire breaks in some of the main cables that were original to the structure, and evidence of significant slippage in several sockets holding the remaining auxiliary cables that were added during repairs in the 1990s, which added weight to the instrument platform.

Thornton Tomasetti, an engineering firm hired by UCF to evaluate the structure, found that given the likelihood of another cable being damaged, the telescope’s repair work – including mitigation measures to stabilize it for further work – would be dangerous. Stress tests to capture a more accurate measure of the strength of other cables can destroy the structure, Thornton Tomasetti found. The company recommends controlled demolition to eliminate the risk of unexpected collapse.

“Although we are saddened to make this recommendation, we believe that the structure should be demolished in a controlled manner as soon as possible,” reads the recommendation for a letter of action provided by Thornton Tomasetti. “That is why we recommend planning the expeditious decommissioning of the observatory and carrying out a controlled demolition of the telescope.”

UCF has hired two other engineering companies to provide assessments of the situation. Immediate stabilizing action is recommended. The other, after reviewing Thornton Tomasetti’s model, agreed that there was no course of action that could safely check the stability of the structure, and recommended that no personnel be allowed on the telescope’s platforms or towers.

“Critical work remains to be done in the fields of atmospheric sciences, planetary sciences, radio astronomy and radar astronomy,” said UCF President Alexander N. Cartwright. “UCF is ready to use its experience with the observatory to join other stakeholders in pursuing the kind of commitment and funding needed to continue and build on Arecibo’s contribution to science.”

After receiving the agreed assessments, NSF hired an independent engineering firm and the Army Corps of Engineers to review the findings. The hired company NSF agreed with Thornton Tomasetti’s recommendations and expressed concern about the significant danger of uncontrolled collapse. The Army Corps of Engineers recommended gathering additional photographic evidence of the facility and a full forensic assessment of the broken cable.

Given the fact that any stabilization or repair scenario will require workers to be at or near the telescope structure, the degree of uncertainty about cable strength and extreme operating forces, NSF accepted the recommendation to prepare for a controlled decommissioning of the 305- meters telescope.


Media contacts

Media Relations, NSF, (703) 292-7090, Email: media@nsf.gov

The American National Science Foundation is pushing the nation forward by advancing in basic research in all areas of science and engineering. NSF supports research and people by providing facilities, tools, and funding to support their ingenuity and support the United States as a world leader in research and innovation. With a budget for fiscal year 2020 of $ 8.3 billion, NSF funds reach all 50 countries through grants to nearly 2,000 colleges, universities and institutions. Each year, NSF receives over 40,000 competitive offers and makes about 11,000 new awards. These awards include support for collaborative research with industry, Arctic and Antarctic research and operations, and U.S. participation in international scientific efforts.

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