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Iconic Arecibo Observatory’s 57-year-old telescope suffers catastrophic collapse ahead of planned demolition 

No injuries were reported as a result of the collapse, but it caused damage to the observatory dish and surrounding facilities

The Arecibo Observatory’s iconic telescope is gone. Ending its 57-year run, the telescope collapsed ahead of its planned decommissioning. The instrument platform of the 305-meter or 1000-feet telescope fell at approximately 7.55 am Atlantic Standard Time on December 1, resulting in damage to the dish and surrounding facilities. No one was injured, informed the National Science Foundation (NSF).

Constructed in 1963, one of the world’s most powerful telescope consisted of a radio dish with a 900-ton instrument platform hanging 450 feet above. The platform was suspended by cables connected to three towers. 

The investigation into the exact details of the platform’s fall is still ongoing. However, engineers assessed the damage and initial findings suggest that the top section of all three of the telescope’s support towers broke off, sending the instrument platform plummeting down to the dish below. As the platform fell, the telescope’s support cables also dropped. The Gregorian Dome is in the dish and the platform is lying on the edge of another side of the dish. The observatory’s learning center, located near Tower 12, appeared to sustain heavy damage from falling cables. While the telescope dish sustained heavy damage, some parts remain intact.

NSF tweeted that it is saddened by this development and will look for ways to assist the scientific community and maintain its strong relationship with the people of Puerto Rico.

NSF Director Sethuraman Panchanathan also said, “We are saddened by this situation but thankful that no one was hurt. When engineers advised NSF that the structure was unstable and presented a danger to work teams and Arecibo staff, we took their warnings seriously and continued to emphasize the importance of safety for everyone involved. Our focus is now on assessing the damage, finding ways to restore operations at other parts of the observatory and working to continue supporting the scientific community and the people of Puerto Rico.” 

What happened earlier?

On August 10, 2020, an auxiliary cable failed, slipping from its socket in one of the towers and leaving a 100-foot gash in the dish below. NSF authorized Arecibo Observatory to take all reasonable steps and use available funds, which amounted to millions of dollars, to secure the analysis and equipment needed to address 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 NSF subsequently ordered the area around the telescope to be cleared of unauthorized personnel.

The second broken cable was unexpected -- engineering assessments following the auxiliary cable failure had indicated the structure was stable and the planning process to restore the telescope to operation was underway. Engineers subsequently found this 3-inch main cable snapped at about 60% of what should have been its minimum breaking strength during a period of calm weather, indicating that other cables may be weaker than expected. 

Multiple assessments by independent engineering companies determined that the telescope could collapse because it is “in danger of catastrophic failure.” They warned that the cables may no longer be capable of carrying the loads they were designed to support. Accordingly, the NSF announced on November 19 that it will begin plans to decommission and dismantle the telescope, which has served as a world-class resource for radio astronomy, planetary, solar system, and geospace research for nearly six decades.

Since NSF announced its plan to pursue decommissioning, surveillance drones found wire breaks on two additional cables attached to the same tower. One showed between 11-14 broken exterior wires as of November 30 while another showed about eight. Each cable is made up of approximately 160 wires. Engineers could not determine whether any internal wires have broken before the failure.

What will happen now?

According to scientists, the top priorities currently include maintaining safety at the site, conducting a complete damage assessment as quickly as possible, and taking action to contain and mitigate any environmental damage caused by the structure or its materials. While the telescope was a key part of the facility, the observatory has other scientific and educational infrastructure that the foundation will work to bring back online.

“We knew this was a possibility, but it is still heartbreaking to see. The safety of personnel is our number one priority. We already have engineers on-site to help assess the damage and determine the stability and safety of the remaining structure. We will continue to work with the NSF and other stakeholders to find ways to support the science mission at Arecibo,” noted Elizabeth Klonoff, vice president for research at the University of Central Florida (UCF), which manages the facility for the NSF. 

Workers at the observatory will wear appropriate safety gear while a full assessment of the site’s safety is underway. Once safety on site is established, other work at the observatory will be carried out as conditions permit. The NSF will continue to authorize UCF to pay Arecibo staff and take actions such as repairing the observatory’s 12-meter telescope and the roof of its LIDAR (light detection and ranging) facility, a valuable geospace research tool.