The end is near for famed Arecibo Observatory’s damaged telescope

After decades of aiding astronomical discoveries, one of the most powerful telescopes on Earth will cease its observation of the universe after sustaining irreparable damage.

The 305-meter telescope at Arecibo Observatory in Puerto Rico will be decommissioned, according to an announcement made by the US National Science Foundation on Thursday.

The spherical radio/radar telescope includes a radio dish 1,000 feet across and a 900-ton instrument platform suspended 450 feet above it. Cables connected to three towers hold the telescope in place.

An auxiliary cable came loose from a socket on one of the towers in August, creating a 100-foot gash in the dish. Engineers were assessing and working on a plan to repair the damage when another main cable on the tower broke on November 6.

When it broke, the cable crashed into the reflector dish below, causing additional damage.

After the break on November 6, engineers inspected the rest of the cables and discovered new breaks as well as slippage from some of the sockets on the towers. Multiple engineering companies reviewed the damage. They determined that the telescope could collapse because it is “in danger of catastrophic failure” and the cables are weaker than expected.

Even if engineers could safely fix all the damage and add cables to support the telescope, it would likely have stability issues in the future.

The latest review revealed that damage to the telescope could not be stabilized without risking staff and the construction team. This led to the NSF making the decision to decommission the telescope after 57 years.

“NSF prioritizes the safety of workers, Arecibo Observatory’s staff and visitors, which makes this decision necessary, although unfortunate,” said NSF Director Sethuraman Panchanathan in a statement.

“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.”

While no direct cause for the breaks has been identified, corrosion is suspected as the main issue. The observatory has withstood hurricanes, earthquakes and tropical storms over the years.

The observatory, which was featured in the James Bond film “GoldenEye,” was completed in 1963 and has been helmed by the NSF since 1970. It is operated and managed by a team at the University of Central Florida, the Universidad Ana G. Méndez and Yang Enterprises Inc.

The telescope has supported and contributed to important discoveries in radio astronomy as well as planetary and solar system research, including gravitational waves.

The Arecibo telescope played a key role in discovering the first planet outside our solar system and has helped astronomers identify potentially hazardous asteroids en route to Earth.

“Until these assessments came in, our question was not if the observatory should be repaired but how. But in the end, a preponderance of data showed that we simply could not do this safely. And that is a line we cannot cross,” said Ralph Gaume, director of NSF’s Division of Astronomical Sciences, in a statement.

A legacy of discoveries

Over the years, Arecibo Observatory has revealed new details about our planet’s ionosphere, the solar system and worlds beyond it.

Observations made by the telescope helped discover the first binary pulsar in 1974 (which led to the 1993 Nobel Prize in physics), supported NASA’s Viking mission, produced the first radar maps of Venus’ surface and spotted the first exoplanet in 1992.

More recently, Arecibo detected organic molecules in a distant galaxy and discovered the first repeating fast radio burst.

“Over its lifetime, 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,” said Michael Wiltberger, head of NSF’s Geospace Section, in a statement.

Fortunately, archival data from the telescope will be migrated to servers outside of the danger zone, continuing the tradition of research and discovery by the telescope for years to come.

End of an era

While the telescope will be decommissioned, the NSF plans to preserve as much of the observatory as it can. This will allow the observatory to serve as a hub for research and education in the future.

The process to decommission a telescope is a complicated one. The NSF plan must meet legal, safety, cultural and environmental requirements. Drones will provide photo surveys that help with the planning. Further evaluations of the broken cable will be conducted, only if they can be carried out safely, to see if they can glean more evidence that could shape their plans.

But any “stress tests” of the cables are being avoided because they could collapse the telescope.

Any part of the observatory at risk of a collapse has been evacuated and will stay closed. The operators of the observatory are hoping to move quickly but thoroughly through their plans to avoid a collapse.

Once the plans are in place, the telescope will be disassembled through a controlled demolition.

“We believe the structure will collapse in the near future if left untouched,” according to a letter by engineering firm Thornton Tomasetti. “Controlled demolition, designed with a specific collapse sequence determined and implemented with the use of explosives, will reduce the uncertainty and danger associated with collapse.”

The firm also recommended that this be carried out “as soon as pragmatically possible.”

After this undertaking is complete, the NSF plans to focus on restoring operations at the observatory.

Of interest is the LIDAR geospace research facility, the visitor center and the offsite Culebra facility for analyzing precipitation and cloud cover data. The NSF is also considering expanding the learning center, although the ongoing pandemic will impact that for the time being.

“NSF recognizes the cultural and economic significance of Arecibo Observatory to Puerto Rico, and how the telescope serves as an inspiration for Puerto Ricans considering education and employment in STEM,” according to a release from the agency.