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Observatory Collapses in Puerto Rico

Wednesday, December 9, 2020

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Following weeks of concern over the possibility of cable failure, the Arecibo Observatory collapsed at the beginning of December, ending nearly 60 years of research at what was once the world’s largest single-dish radio telescope.

According to the National Science Foundation, who oversaw the National Astronomy and Ionosphere Center under a cooperative agreement by the University of Central Florida, no injuries were reported.

About Arecibo

In the late 1950s, Cornell University physicist William E. Gordon conceived the idea for the observatory to further explore the Earth’s atmosphere and the composition of nearby planets and moons. While the construction of the infrastructure wasn’t completed until 1963, Cornell astronomy professor Martha Haynes reports that the location in Puerto Rico was chosen for its “vicinity to the equator and of the topography of the terrain, which provided a nearly spherical valley and minimized excavation.”

Built within a karst sinkhole, the dish’s surface is comprised of some 30,000 perforated aluminum panels aligned in an inverted spherical dome shape stretching 1,000 feet in diameter. Hanging above the dish is the observatory’s 900-ton radio telescope, suspended by a series of cables attached to surrounding support towers.

According to NPR, the telescope underwent major upgrades in the 1970s and 1990s, allowing researchers to expand the observatory’s role in research. The structure was built and maintained with federal funds and was managed for the first few decades of its service by Cornell until the UCF took on the role sometime later.

In 1993, Russell Hulse and Joseph Taylor were awarded the Nobel Prize in Physics 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.

Throughout its life, Arecibo was also used by NASA to characterize asteroids that could pose a threat to earth through the agency’s Near-Earth Object Observations Program in the Planetary Defense Coordination Office and has even been featured in the X-Files, GoldenEye, and Contact.

The famed infrastructure has also withstood its fair share of natural disasters, most notably Hurricane Maria in 2017 and a series of earthquakes, it wasn’t until Aug. 10 of this year where one of the Tower 4 auxiliary cables that supports the telescope’s platform experienced a failure that resulted in damage to the telescope’s primary reflector dish and the Gregorian dome that things started to go downhill for the observatory.

In management update following the incident, Director Eng. Francisco Cordova reported that the telescope was moved into its “stow/safe” position in order to reduce the loads experienced by the Tower 4 cables and to ensure no movement of the azimuth during heavy wind events.

At the time, officials had met with dozens of experts regarding the infrastructure’s suspension cables fabrication and installation, structural analysis and forensic investigation, among other topics, but by the end of August, had yet to determine the cause of the cable’s failure. Cordova reported that the lack of findings was due to the inability to retrieve a portion of the failed cable and socket for forensic analysis and investigation because there was no comprehensive safety plan for personnel to retrieve those items.

By Aug. 17, the telescope was taken offline, and the facility was in the process of having a detailed structural model of the infrastructure made to reflect its current state. The following month, the socket involved in the cable failure was removed and its hardware was shipped to Florida for forensic evaluation at the NASA Kennedy Space Center where experts planned to conduct nondestructive analysis and tests in conjunction with the forensic engineering firm leading the investigation.

In October, the structural model was completed, as were cable sag surveys for all auxiliary cables. Additionally, teams installed an instrumentation system, which was slated to continually monitor the condition of the structure, completed a safety assessment plan. The NSF was also reported to have completed a review of a temporary repair plan. The plan called for temporary friction clamps to be installed at two backstay cable locations and were meant to bypass the cable load as a precaution in case the cables failed again at their sockets. 

However, these efforts proved useless and at the beginning of November, another main cable at the facility broke, crashing onto the infrastructure’s reflector dish below, causing additional damage to the dish and other nearby cables. Unlike the previous case with the socket issue, officials believed that the failure was related to the extra load the remaining cables have been carrying since the previous break in August, in addition to suspected degradation.

At the time, UCF issued a supplemental funding request for temporary repairs related to the original break, however, there was no cost estimate for the repairs.

By the middle of November, engineering firms investigating the cable failures and the integrity of the remaining cables reported that the situation posed a serious safety risk to employees and contractors as the chances of another break have only continued to increase.

On Nov. 19, the NSF announced that it planned to decommission the Arecibo Observatory following the recommendation of the engineer of record, Thornton Tomasetti, who found the structure to be in danger of catastrophic failure. The NSF reportedly had two other groups review the structure as well, reaching the same conclusion as Tomasetti.

“Our team has worked tirelessly with the NSF looking for ways to stabilize the telescope with minimal risk,” says UCF President Alexander N. Cartwright at the time. “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.”

Capturing the Collapse, What’s Next

On Dec. 1, the day of Arecibo’s collapse, a set of cameras recorded the fall of the infrastructure, one taken from the ground at the observatory’s Operations Control Center, and another mounted on a drone located above the platform.

In the video, viewers are met with the moment where multiple remaining cables snapped, causing the telescope platform to swing outwards and down into the side of the dish below. The other cables that did not fail in the structure’s collapse ended up pulling down the tops of the three support towers surrounding Arecibo.

“The cables that go from the top of Tower 4 to the platform—they’re very faint in the camera view but they’re there,” said John Abruzzo, a contractor at Thornton Tomasetti. “And so it’s those cables that fail near the tower top first, and then once those fail, the platform then loses stability and starts to come down.”

Because NSF was unable to decommission the infrastructure prior to its collapse, its now working to develop a new plan on how the Arecibo can be cleaned up in a safe manner. To do so, engineers will have to first conduct a full environmental assessment of the area and determine the stability of the remaining structures.

“With regards to replacement, NSF has a very well-defined process for funding and constructing large scale infrastructure—including telescopes,” said Ralph Gaume, Director of NSF’s Division of Astronomical Sciences. “It’s a multi-year process that involves congressional appropriations, and the assessment and needs of the scientific community. So it’s very early for us to comment on the replacement.”


Tagged categories: Accidents; Asia Pacific; Corrosion; EMEA (Europe, Middle East and Africa); Health & Safety; Health and safety; Infrastructure; Latin America; National Science Foundation; North America; Project Management; Z-Continents

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