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Last summer, the Arecibo Observatory suffered severe damage when an auxiliary cable supporting the platform above the telescope broke and hit the reflector. Soon after, technicians from the observatory and the University of Central Florida (UCF) began work to stabilize the structure and assess the damage. Unfortunately, about two weeks ago (on November 6th), a second cable broke causing even more damage.
Following an in-depth review, the US National Science Foundation (NSF) announced that the observatory cannot be stabilized without risking the lives of construction workers and facility staff. Therefore, after 57 years of loyal service and countless contributions to multiple fields of astronomy, the NSF has decided to initiate plans to decommission the Arecibo Observatory.
This decision came shortly after NSF evaluated the assessments of a number of independent experts and companies to determine the cause of the structural failures and recommend measures to make repairs. These assessments indicated that the support cables are no longer able to carry the required loads and that the telescope structure is in danger of catastrophic failure.
Furthermore, several evaluations have stated that any attempt to carry out repairs could endanger workers’ lives. They also found that even if the repairs were successful, the structure would still suffer from long-term stability issues. As director Sethuraman Panchanathan said in an NSF statement:
“NSF prioritizes the safety of workers, Arecibo Observatory personnel and visitors, which makes this decision necessary, albeit unfortunate. For nearly six decades, the Arecibo Observatory has served as a beacon for revolutionary science and what a partnership with a community can be like. While this is a profound change, we will look for ways to assist the scientific community and maintain that strong relationship with the people of Puerto Rico. “
After the first accident, engineering teams wasted no time in developing an emergency stabilization plan for the auxiliary cable system. Despite the damage caused by the breakage of the auxiliary cable to the Gregorian dome, the supporting structure and the 30 meters (100 feet) gash left in the reflector, the engineers were ready to begin repairs by 9 November (three days after the second cable Broken).
The observatory was also arranging the delivery of two replacement (and two temporary) auxiliary cables when the second failure occurred. This time it was a main cable that broke, indicating that the structural problems extended to all the networks of cables connecting the main dish to the instrument platform above it.
According to Ralph Gaume, director of the NSF’s Division of Astronomical Sciences, this was the deciding factor in the decision to dismantle:
“The leadership of the Arecibo Observatory and UCF have done a commendable job addressing this situation, acting quickly and pursuing every possible option to rescue this incredible tool. Until these assessments came, our question was not whether the observatory should be repaired, but how. But in the end, a preponderance of data showed that we simply couldn’t do it safely. And this is a line that we cannot cross “.
Engineering evaluations quickly followed which indicated that this 7.62 cm (3 inch) main cable was subjected to stresses up to about 60% of its minimum tolerance (during calm weather) when it broke. Inspections of the other cables revealed new wire breaks on some of the other main cables and evidence of significant slippage in several outlets holding the remaining auxiliary cables.
These results confirmed that both the main and auxiliary support cables were weakened more than originally expected. This led the engineering teams to conclude that decommissioning and demolition were the only option. John Abruzzo was responsible for the evaluation done by Thornton Thomasetti, one of the structural engineering companies that evaluates the observatory. As he summarized in their letter of recommendation for action:
“While we are saddened to make this recommendation, we believe the facility should be demolished in a controlled manner as soon as pragmatically possible. Therefore, it is our recommendation to quickly plan the decommissioning of the observatory and carry out a controlled demolition of the telescope. “
NSF’s plan to dismantle the observatory would involve shutting down the 305 m (100 ft) telescope while safely preserving other parts of the observatory that could be damaged or destroyed in the event of a catastrophic failure. In short, they hope to retain as much of the remaining infrastructure as possible so that it can still be used for future research and educational purposes.
The decommissioning process is complex and requires the NSF, UCF and all participating institutions to comply with a range of legal, environmental, safety and cultural requirements. Meanwhile, NSF has initiated a high-resolution photographic investigation using aerial drones and is considering conducting a forensic assessment of the broken cable (assuming it can be done safely).
When all the necessary preparations are finished, the telescope will be subject to a controlled disassembly. Once this is done, NSF intends to restore operations at the Arecibo LIDAR facility, its visitor center, and the offsite Culebra weather facility. The analysis and cataloging of archival data collected by the telescope will also continue.
While the deactivation of Arecibo is certainly a sad development, it is clearly needed at this juncture. Michael Wiltberger, head of NSF’s geospatial section, said:
“Over the course of its lifetime, the Arecibo Observatory has helped transform our understanding of the ionosphere, showing us how density, composition and other factors interact to shape this critical region where Earth’s atmosphere meets space.
“While I am disappointed with the loss of investigative capacity, I believe this process is a necessary step to preserve the ability of the research community to use the other resources of the Arecibo Observatory and hopefully ensure that important work can continue at structure”.
During its 57 years of service, the Arecibo Observatory was the world’s first radio telescope and one of the most iconic astronomical structures in the world. Until the completion of the 500-meter Aperture Spherical Telescope (FAST) in China, it was also the largest radio observatory in the world. Its results are unmatched and include a number of firsts.
These include confirmation of neutron stars, detection of the first binary pulsar, the first millisecond pulsar, and the first exoplanets. The facility also hosts the Planetary Radar Project which (with support provided by NASA’s Near-Earth Object Observations Program) tracks and characterizes near-Earth (NEO) objects. In addition, the facility also played an important role in Extraterrestrial Intelligence Research (SETI).
In addition to providing the source data for [email protected] and the SETI Institute’s Pheonix project, the observatory is also one of the few installations in the world to actively send a coded message into space intended for extraterrestrials. – aka. the message of Arecibo. He has done so much in his life and will continue to contribute in retirement.
So far, Arecibo! We will miss you!
Further reading: NSF
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