For 57 years the Arecibo Observatory has served as a world-class resource for radio astronomy and planetary, solar system and geospace research. UCF remains committed to the scientific mission in Arecibo and to the local community .

Arecibo Observatory Telescope to be Decommissioned After Second Cable Break

By: Zenaida Gonzalez Kotala on

Following a review of engineering assessments, the U.S. National Science Foundation today announced it will begin planning the controlled decommissioning of the 1,000-foot-wide telescope at the Arecibo Observatory in Puerto Rico.

The observatory, which UCF manages for NSF under a cooperative agreement, has for 57 years served as a world-class resource for radio astronomy and planetary, solar system, and geospace research. But a main cable break on Nov. 6 caused the structural integrity of the telescope to come into question.

Three engineering firms, which had been previously hired to address an auxiliary cable break at the facility in August, assessed the telescope and submitted their reports to NSF. The engineer of record, Thornton Tomasetti, recommended decommissioning of the telescope because it found the telescope structure is in danger of a catastrophic failure. NSF had two other groups review the assessments, and they concurred that pursuing repairs posed a risk to human life.

“Our team has worked tirelessly with the NSF looking for ways to stabilize the telescope with minimal risk,” says UCF President Alexander N. Cartwright. “While this outcome is not what we had been working towards, and we are disheartened to see such an important scientific resource decommissioned, safety is our top priority. At a time when public interest and scientific curiosity about space and the skies has re-intensified, there remains much to understand about the data that has been acquired by Arecibo. Despite this disappointing setback, we remain committed to the scientific mission in Arecibo and to the local community.”

UCF will work with NSF to implement the safety plans and authorizations needed to begin the decommissioning process. The work is not expected to begin for several weeks. The goal is to bring down the telescope, which includes the platform and Gregorian Dome and keep as many other parts of the facility intact for future use.

NSF says it intends to restore the LIDAR facility, which is used in geospatial research at Arecibo as well as the visitor center and the offside Culebra research substation, which analyzes cloud cover and precipitation data.

“NSF prioritizes the safety of workers and Arecibo Observatory’s staff and visitors, which makes this decision necessary, although unfortunate,” said NSF Director Sethuraman Panchanathan. “For nearly six decades, the Arecibo Observatory has served as a beacon for breakthrough science and what a partnership with a community can look like. While this is a profound change, we will be looking for ways to assist the scientific community and maintain that strong relationship with the people of Puerto Rico.”

Arecibo’s Beginnings

The Arecibo Observatory was constructed from 1960 to 1963 and was the brainchild of Cornell University Physicist William Edwin Gordon. Cornell University was the first manager of the site. The location was ideal for the telescope and would lead to decades of significant contributions in the areas of atmospheric sciences, planetary sciences, radio astronomy and radar astronomy.

AO’s telescope’s huge primary disc has been a workhorse for science. It was used to discover the first exoplanets and detect organic molecules outside our galaxy. The 1993 Nobel Prize in Physics was awarded to Russell Hulse and Joseph Taylor for their work with Arecibo in monitoring a binary pulsar, providing a strict test of Einstein’s theory of general relativity and the first evidence for the existence of gravitational waves. Arecibo also helps NASA characterize asteroids that could pose a threat to earth through the agency’s Near-Earth Object Observations Program in the Planetary Defense Coordination Office. The facility even appeared in a James Bond film and The X-Files television series.

Considered a cultural treasure in Puerto Rico, the site is visited by thousands of school children each year and thousands of other visitors from around the world. The visitor center, built through private donations, also conducts several education outreach programs throughout the year that impact all learners. NSF supports a Research Experience for Undergraduates program there each summer.

UCF became the facility’s manager in April 2018 after being awarded a $20.15 million, five-year grant. This is year three of the grant. Since coming onboard with UCF, the facility secured new funding to continue NASA’s work and to design and guide new instruments that were scheduled to be added to the telescope over the next few years. Other scientists also secured funding to enhance Arecibo including a 2018 grant awarded to Brigham Young University and Cornell University for $5.8 million to design and mount a supersensitive antenna (ALPACA) at the focal point of the telescope’s dish.

In 2019, UCF expanded its agreement with Microsoft, which resulted in the observatory getting access to a variety of Azure services –– from analytics to artificial intelligence –– to develop a new platform that will help facilitate access and storage of the 12 petabytes of data the observatory has collected in its 50-year history. Once fully implemented, the new platform is expected to make robust information about planets, pulsars, asteroids and comets more easily accessible to scientists working at Arecibo and around the world. The work is underway.

The observatory continued to help scientists with observations that they turned into published journal articles and which expanded our knowledge of space and Earth’s place in the solar system.


The facility has endured several hurricanes and earthquakes. It was damaged during hurricane Maria in 2017, and the Federal Emergency Management Agency used the observatory’s helicopter landing pad and other facilities as a staging ground to get supplies and help to the community. UCF worked to secure funding to make repairs and improve the site after the hurricane. The work was ongoing when the first auxiliary cable broke in August 2020.

The cable slipped from its socket in one of the towers, leaving a 100-foot gash in the dish below. A team of experts were called in to investigate the cause of the break and figure out a way to make repairs. UCF worked with NSF to assess the break and come up with a plan. The facility was closed, and a monitoring team began watching all the cables and platform as part of the facility’s safety and temporary emergency repair plan. Safety was the priority throughout the assessment process. Arecibo was awaiting a team of engineers who were expected to begin temporary emergency repairs related to the August incident when the main cable broke on Friday, Nov. 6.

Unlike the auxiliary cable that failed, this main cable did not slip out of its socket. It broke and fell onto the reflector dish below, causing additional damage to the dish and other nearby cables. Both cables were connected to the same support tower. A safety zone was set up around the dish and only personnel needed to respond to the incident were allowed onsite.

The second broken cable was unexpected. Engineering assessments following the auxiliary cable failure indicated that the structure was stable, and the planning process to restore the telescope to operation was underway. Engineers subsequently found the 3-inch main cable snapped at about 60 percent of what should have been its minimum breaking strength during a period of calm weather, raising the possibility of other cables being weaker than expected. Subsequent inspections via drones of the other cables revealed new wire breaks on some of the main cables.

All the information was shared with NSF, which notified UCF of its decision on Nov. 18. Next steps are still pending, and UCF is committed to working with the Puerto Rican community.

“Critical work remains to be done in the area of atmospheric sciences, planetary sciences, radio astronomy and radar astronomy,” President Cartwright says. “UCF stands ready to utilize 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 contributions to science.”

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