As cleanup operations are underway at Arecibo Observatory in Puerto Rico, some scientists are proposing a replacement for the esteemed radio dish.

The National Science Foundation (NSF) made a report to Congress last week that details the damage to the 1,000-foot radio telescope following the collapse of the 900-ton instrument platform that was suspended above the aluminum dish. The report revealed details about the events leading up to the collapse, as well as a look forward to what’s next for the Arecibo Observatory.

Even as some of Arecibo’s operations continue, the NSF is considering its options for repairing other capabilities. Meanwhile, a group of scientists and engineers is proposing not just repairs but a full-on replacement that promises a dramatic increase in power and sensitivity.

The Collapse

Arecibo dish damage
This image shows the damage wrought by the first cable failure on August 6th.

The NSF report outlines a detailed timeline of events:

  • August 10, 2020, 3 a.m. ET
    An auxiliary cable from Tower 4 pulls loose from its socket. The cable falls onto the dish below, damaging some 250 of 40,000 aluminum tiles that make up the reflective dish.
  • August and September
    Engineers model support structures and determine a safety plan in order to access the failed socket on Tower 4. They also develop a stabilization plan for repairs.
  • End of September
    NSF authorizes an order for replacement cables, due to arrive in December. Stabilization efforts prior to replacement are set to begin November 9th.
  • Early October
    Engineers remove the failed socket and send it to the NASA Kennedy Space Center for analysis.
  • November 6, 2020, 8:15 p.m.
    A main cable from the same tower, Tower 4, breaks.
  • November 19, 2020
    NSF announces that the 305-meter radio telescope will have to be dismantled, as repairs cannot be made without jeopardizing safety.
  • November 24, 2020
    NSF confirms that additional wires within the thick cables are continuing to snap.
  • December 1, 2020, 7:00 a.m.
    The remaining cables from Tower 4 snap and the suspended platform crashes down on the dish below, causing extensive damage.

The collapse also ripped off the top 18 meters (60 feet) of Towers 4 and 12, and the top 37 meters of the taller Tower 8. Outside of the dish, towers, and other support structures, damage was surprisingly limited, mostly to building roofs. A number of the observatory’s facilities, including LIDAR and optics to observe the atmosphere as well a 12-meter radio telescope, are still operational.

NSF states that investigation into the collapse is ongoing. Engineers continue to investigate the failed socket involved in the auxiliary cable’s loss as well as the main cables, which NSF says were “weaker than expected.” The main and auxiliary cables date to the 1960s and the 1990s, respectively. NSF expects to have final reports on these investigations by December 2021.

Arecibo damage
This photo taken on December 8, 2020, shows damage to the 305-meter telescope at Arecibo Observatory, after its collapse a week earlier. The remains of the instrument platform are visible on the telescope’s dish.
Michelle Negron / National Science Foundation

The Repairs

Cleanup has begun, but it’s a long process that will continue into 2022, costing some $30–50 million. Engineers have mapped the debris from the collapse and workers have made good progress, as can be seen in the overhead image below. Cleanup isn’t only about removing machinery; there are environmental effects, too. For example, workers are also excavating soil contaminated with hydraulic oil released during the collapse.

Overhead view of Arecibo cleanup
This overhead view of Arecibo's 305-meter dish, provided as part of the NSF report, shows the cleanup process already underway. Workers have removed much of the debris, exposing the ground beneath, and allowing access to the collapsed platform at the upper left of the dish.

Anything that’s still scientifically usable is staying put, though, as NSF is still deciding how to proceed with repairs. The organization is convening a meeting of scientists and engineers in the April timeframe to consider next steps.

One option on the table is to rebuild the 305-meter reflecting dish and continue studies of Earth’s atmosphere using instruments like the High Frequency ionospheric heaters and incoherent scatter radar.

But to conduct astronomy or planetary studies, the dish would have to be replaced. Some, led by Arecibo senior scientist Anish Roshi, are proposing a replacement that would be vastly different — and more powerful — than what’s there now.

A Replacement

Here’s the idea as outlined in a white paper circulated by Roshi and his colleagues: The Next Generation Arecibo Telescope would pack hundreds, maybe even more than 1,000 smaller radio dishes into the same space now occupied by the single 305-meter dish. Those smaller antennas would combine forces to act like a single larger telescope (no suspended instrument platform required).

Ideally, those dishes would be on a single, tiltable platform to access more of the sky from the Arecibo site; it’s possible multiple platforms could do the same.

Next Generation Arecibo Telescope  possible designs
Two possible designs of the Next Generation Arecibo Telescope are shown here: 1,112 parabolic reflectors that are each 9 meters in diameter (left) or 400 dishes 15 meters in diameter (right). In both cases shown here, the arrays are placed on a single, tiltable platform.
Roshi et al. / arXiv

The revamped telescope would have twice the sky coverage of the legacy dish, 500 times the field of view in individual images, at least double the sensitivity, and five times the radar power.

Those new capabilities open up a lot of new science. For example, the increased sky coverage would put the galactic center in view, allowing astronomers to search for pulsars orbiting the supermassive black hole lurking there and enabling unprecedented tests of general relativity.

A rough estimate puts the cost of such a facility at $454 million, less than the cost of producing and marketing Avengers: Endgame. A truer estimate will come once the telescope’s design is hammered out.

“The Next Generation Arecibo Telescope will not start from scratch,” the team states on their website. “It will take advantage of the existing infrastructure, decades of experience, and the support of the local people and government.”

Pluton space radar
The Pluton radar system in Crimea consists of eight reflectors, each 16 meters in diameter. It serves as a working example of a compact dish array mounted on a plane.
Rumlin / Wikimedia Commons / CC BY-SA 3.0

To Be Decided

The plan is exciting to be sure, but the final decision is likely a long way off.

“NSF has a very well-defined process for funding and constructing large scale infrastructure, including telescopes,” said Ralph Gaume, director of NSF’s astronomy division. “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.” While Gaume issued that statement at a December press conference, it’s no less true now.

And it’s worth keeping in mind that in addition to any Arecibo repairs, NSF also needs to fund the under-construction Vera C. Rubin Observatory, the just-commissioned Daniel K. Inouye Solar Telescope, the ALMA radio array in Chile, the LIGO gravitational-wave detectors, and several other facilities. All those big, expensive instruments compete for the same available funds.

A separate Congressional appropriation is theoretically possible — that’s what helped rebuild the 100-meter Green Bank Telescope following its unexpected collapse in 1988. The political realities are a bit different in Puerto Rico than in West Virginia, but a number of representatives have expressed support for rebuilding Arecibo.

The astronomy community’s decadal survey, which outlines funding priorities for the next 10 years (or more) and is due out in the next couple months, may also play a role in deciding Arecibo's fate.

In the meantime, NSF is considering all proposals — the floor is open.




Image of Michael-Finkelstein


March 11, 2021 at 10:38 am

I'm all for a new large radio telescope but it seems to me neither of the two possible ideas illustrated are designed to take advantage of the bowl shaped depression of the Arecibo site and more importantly wouldn't necessarily need to be located there at all. I'm no engineer but wouldn't a single tiltable platform on which the new array would be mounted require it to be on a plane which would therefore make a flat desert location more suitable and less expensive to construct?

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March 11, 2021 at 7:43 pm

If they are lining the bowl, then they will be blocked when targetting to the side. Imagine a salad bowl with a plate on top. That can be tilted so the whole plate faces a target. The depression would act as the rails for the alt/azi bearings. And it would be better than a flat area since you get the full aperture when you tilt the plane vs tilting the dishes.

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Image of DavGold


March 11, 2021 at 6:03 pm

Personally, I want this telescope rebuilt and upgrade. It's sad to see this piece of infrastructure left to just fall apart.

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Image of Michal


March 12, 2021 at 8:56 pm

I wish it were possible to honor the rich tradition at Arecibo, but seems like it would be folly to rebuild on a site that is expected to see more frequent powerful hurricanes in the future. I'm curious to see if that can be mitigated or whether this happens at all.

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Image of Alan Potts

Alan Potts

March 13, 2021 at 9:20 pm

I lived, as a child, with Jodrell Bank radio telescope on the horizon of the Cheshire Plain, in England.

That nurtured my taste for science.

Arecibo is a natural formation. It should be used. It has served mankind through the last several decades because it is what it is.
A natutural radio telescope.

Maybe use a high resolution link with the VLA?

In fact it is a gift to astreonomy, whatever.

Maybe a part of an international VLBI collaboration which may help the aching hearts of Congress, given the Covid-19 situation.
$$...always persuades them!

My epitaph.

We are only born once.
We see the sky.
We see the Universe.
We think.
We die.

Arecibo is a gift for all humanity.

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Image of Howard Ritter

Howard Ritter

March 18, 2021 at 9:25 am

Bill Gates, Paul Allen Foundation, Elon Musk, Jeff Bezos – how about committing a few rounding errors next time you tally your fortunes, and earmark a trivial half-billion for naming rights to the new instrument?

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