NSF Releases Video Of Arecibo’s Final Moments

Today the National Science Foundation released a pair of videos that document the collapse of the Arecibo Observatory with incredible detail. A wide shot, apparently taken from the Visitors Center, shows the 900 ton instrument platform breaking free and swinging on the remaining support cables until it smashes into the edge of the dish. The second clip, recorded by an airborne drone, is focused directly on the cables as they failed. Both can be seen in the video embedded below.

Together, they produce an invaluable visual record of what finally brought the iconic radio telescope down. As was predicted by engineers earlier in the month, the failure of another support cable on tower 4 triggered a chain reaction that brought the entire platform crashing down onto the 305 meter reflector. Footage from a drone observing the top of tower 4 shows that the entire sequence, from the first visual wire break to the remaining cables being torn from their mounts, only took five seconds. While some initially doubted the NSF’s determination that it was too dangerous to repair Arecibo, this footage seems to prove just how tenuous the structural integrity of the Observatory really was.

A drone captured the critical cable failure.

These videos will hopefully help investigators who still need to determine why the cables failed in the first place. The cable in August didn’t snap, it simply pulled lose from its mount. It was suspected that the cable may have been incorrectly installed, but as it was only a backup, the situation was not seen as critical. But when the second cable failed in November it was found to have snapped at just 60% of its minimum breaking strength.

This immediately called into question the condition of the remaining cables, and ultimately lead to the decision by the NSF to proceed with a controlled demolition of the Observatory that would preserve as much of the scientific equipment as possible. Unfortunately, the remaining cables didn’t last long enough to put that plan into action.

After the cleanup, investigators will have the opportunity to examine the cables in an effort to find out what caused their premature failure. Was there some design or manufacturing flaw that meant they were always dangerously overrated? Or perhaps investigators will confirm what many already fear; that humanity has lost a one of a kind scientific instrument due to dwindling financial support and lax maintenance procedures.

82 thoughts on “NSF Releases Video Of Arecibo’s Final Moments

          1. Ah that stupid movie, the whole SETI thing is a fraud. Advanced civilisations don’t need to use radio to communicate, they modulate the smallest and lowest dimensional possible wormhole for the shortest amount of time, because that is energetically feasible, and this causes the quantum foam to experience an event horizon therefore virtual particle pair members are trapped on either side of it so users at either end get one each, and they are entangled too.

      1. Estimates to rebuild were around $100 million in 2001, add some for inflation and we could do it for $250 million.

        That’s actually very little in comparison to other things we’re building (the wall, the Iran agreement), and trivially tiny compared to our military budget.

        Further, rebuilding the observatory would allow us to use more modern materials, and possibly install more modern and interesting receivers.

        (We could film the next James Bond movie there as well!)

        1. just for comparison purposes it cost $200 million to make SpiderMan 2, again this thing could be rebuilt as a movie prop and it can be paid for with popcorn and jumbo soft drinks. Someone at NSF needs to be talking to Marvel or Netflix about movie rights.

          1. Yeah, but $190 million of that went into paying copyright lawyers, rights management organizations, royalties, agents and their actors, and advertising for the movie.

            If Sandra Bollocks appears in the movie, that’s $50 million right off the bat.

        2. It would also employ Puerto Ricans, who really could use money into their economy. Arecibo was a must-see while I was in Puerto Rico and easily contributed to me spending 2x what I would have during that trip. It was one of the technological wonders of the world, I wish more people would have seen it.

          1. A single project to inject money into the economy is not going to sustain employment. It’s like dropping a crate of polished rice into a famished African village vs. seeds and farming equipment. It’s just helicopter humanitarianism. It has it’s place in a disaster, like repairing essential infrastructure in a poor country, but it isn’t justified as it is.

            Economic aid that isn’t actually aid is just popular with politicians, because there’s always going to be demand for it. It’s showing solidarity for the brownie points, but sustaining poverty to ensure continuous re-election. All you have to do then is point fingers at others to explain why you didn’t accomplish anything this time around either.

    1. You could rebuild Tu-154M that crash-landed in Smolensk Intl. but that doesn’t mean you’d find many customers to warrant operating it. Fuel would be too expensive compared to using CASA or C-130. Same deal with Arecibo.

      1. Arecibo was an important scientific instrument, sure we can rebuild it. Bigger, better, more powerful and more useful. And it would be more useful than some old plane used by politicians who don’t care about waste of money…

  1. Yes, to all of the above. I STILL need a new Arecibo T-Shirt. Mine, shrank… really! I’ll take 6 at least.

    From the Golden Gate Bridge to the very new Bay Bridge, suspension cables were/are under spec or poorly/wrongly installed or exposed to corroding elements due to same.

    I am reminded of an astronaut’s responce about his thoughts when being lifted into orbit. “Over 50,000 parts, and all built by the lowest bidder.” So goes the labor as WELL AS parts on these types of projects. PG&E gas pipelines showing re-labled Xray-photoes of good sections representing bad sections. Lower costs fund golden parachutes and/or future work.

    But let’s hear some detail about that *unusually able* drone, eh? Military?

    1. >> From the Golden Gate Bridge to the very new Bay Bridge, suspension
      >> cables were/are under spec or poorly/wrongly installed or exposed to
      >> corroding elements due to same.

      Suspension cables are notoriously difficult to inspect, and if faults are found, are notoriously expensive to fix (they weren’t under load with a bunch of important stuff hanging from them when first built).

      See: Morandi Bridge collapse, Silver Bridge collapse, Nanfango Bridge collapse, Hammersmith Bridge closure… etc.

      Even in situations where you *can* easily replace a cable (like a radio transmitter tower) it’s still difficult enough to inspect them that there still a handful of failures each decade ( Europe 1 longwave tower, Cape Race LORAN station, etc…)

        1. Exactly. How easily people seem to forget that maintenance is an integral part of any step. Including, buildings, facilities (such as this one), ships, airplanes, and on, and on. When the military was done with their part of this, they turned it over to NSF with no funding, no maintenance, no plan, no nothing. Gor 60 years, or so, this facility has performed brilliantly, with an extremely small budget, and now everyone acts surprised at its failure. It d as should be totally rebuilt and fully funded. Certainly a far better investment than presidential golf outings/Nuremberg rallies.

        2. It’s probably more accurate to think of the Morandi Bridge as a cable-stayed structure with the number of stays reduced to the possible minimum, then those stays were embedded in cast concrete.

          The architect, Riccardo Morandi says the concrete was to protect the cables, but most people suspect that he was just into the chunky look, since he built similar bridges in Brazil and Libya.

          The practical effect was to take one of the biggest advantages of the cable-stayed design – the structural redundancy – and negate it by only using one cable in each corner, then embed that cable – now a single point failure – inside a big cement block so it couldn’t ever be inspected again.

          What could possibly go wrong? Especially in a seismically active seaside town with warm, wet summers, on a bridge managed by Atlantia S.p.A., a toll road company known for… let’s say…. aspirational… maintenance schedules.

      1. At least the suspension cables CAN be inspected and fixed somehow.

        Take reinforced concrete. It only works as long as the rebar is intact, and it’s almost perfectly impossible to inspect, and completely impossible to repair. You just have to wait until it starts to crumble and then blow the whole thing to bits, make another.

      2. Silver Bridge was an eyebar chain bridge, not a cable bridge. It would have been easy enough to repair, but the flaw was only detectable by x-ray or disassembling each joint.

        1. Yeah, I knew that, but I thought that the same basic lesson applied, hanging structure, difficult to inspect, expensive to repair if problems are found, etc.

          Though, as an aside, the irony with the Silver Bridge is that there was purposely enough structural redundancy to save the bridge is an eyebar failed. The suspension chains consisted of several links in parallel, with big pins at each joint which also held the descenders. The pins had large end caps attached specifically to retain the links and descenders laterally, but these were attached with a smallish central bolt sized for normal expected loads.

          In the collapse, the eyebar link that failed was on the outside, and the subsequent load transfer twisted the joint and drove the pin sideways. The end cap bolt sheared and released the cap, which allowed subsequent links to slip off.

    2. I am reminded of an astronaut’s responce about his thoughts when being lifted into orbit. “Over 50,000 parts, and all built by the lowest bidder.”

      Wasn’t that Steve Buschemi in Armageddon? “You know we’re sitting on four million pounds of fuel, one nuclear weapon and a thing that has 270,000 moving parts built by the lowest bidder. Makes you feel good, doesn’t it?”

      I really like Peter Stormare’s quote to go along with it “Components? American components, Russian components, all made in Taiwan!”

      1. The original quote is from John Glen, talking about the Mercury/Atlas rocket.
        “I felt exactly how you would feel if you were getting ready to launch and knew you were sitting on top of 2 million parts — all built by the lowest bidder on a government contract.”

        He doesn’t seem to have said it at the time, more likely it was a quip he honed after being asked a thousand times “what was going through your mind while you were waiting for launch?”. I suspect the real (and less interesting) answer was; “checklists”.

        1. Since the reflector is fixed, the receiving antenna has to move around to track an object in the sky, that’s what that big rotation ring and cantilever track did (the big triangle frame itself didn’t move)

          1. Ok, I see now there’s the the ‘slide’ that allows the antenna receiver to move around. Could one put three posts closer to the antenna though, with steel bridges between them that would allow the receiver to move around inside?

          2. Well, given 2020 technology, you could probably loose the big static frame and use a much smaller cable system to just dynamically position an antenna and receiver in the right spot.

            Think something like a giant version of the CableCam systems that are used for sports.

            The vast majority of the suspended weight was a big steel triangle, which held a big steel ring track, which held a big steel cantilever track, on which an antenna and counterweight were moved. If you can cut that down to just the antenna and some LNA’s you’re probably talking about maybe 10% of the original “flown weight”

          3. Steve, you are forgetting the radars that the platform carried. Those powerful radar transmitters were the heaviest part of the instrumentation (and you can’t exactly put them at the end of a waveguide, given the need to move it and the distances involved).

          4. Make a hole in the bottom of the dish and put the transmitter in it. Above it suspend a reflector to bounce the beam. You can change the focal point by tilting the transmitter and tilting and moving your reflector. You can even change the geometry of reflector (make it from a mesh covered with mylar or something and use servos to change its shape) and put receivers next to the transmitter…

          5. @X
            > how much does a microwave transmitter weigh? I have a 1 kW microwave transmitter on my kitchen countertop and it certainly doesn’t weigh 800 tons.

            the good ones do..

      1. Sorry; X says: December 3, 2020 at 8:33 pm ; I thought it was the reply button; clicked report in error.

        The latest transmitter is 1 Megawatt 12.6 cm wavelength. It’s not clear if that is pulse or continuous wave, but that’s a lot of energy into that wavelength.

    1. That’s kind of interesting . . . I wonder what kind of receiver you could loft on a drone. You would get the positioning for free, and all you would need is a dish. Clearly you’re not going to loft 800 tons, but you might be able to loft a few pounds that way.

          1. Hanging up in air for long periods of time not moving much? Why people jump to drones? theres prooven tech that could be used – blimp(for reposition) or baloon on a leash (split it in three and you can change position of it). We could fill it with hydrogen on cheap and double the payload or helium for pricey but safer lower payload. seriously you guys “drone” isn’t always correct answear even if its uber cool, if theres a nail just use hammer not drone or 3d printer contraption.

          1. Although I doubt a drone could carry the needed weight, it’s an interesting idea. You had the receiver suspended on 3 (sets of) cables. If a drone could carry the weight, you could run power up 3 tether cables, and also use them for positioning. So the drone would be overpowered and just pull against the cables. The cables would also help resist effects from wind.

            Although I’m sure a drone would have a failure rate a heck of a lot higher than once in a half century. Sometimes, the best way to do something does turn out to be the way it was done in the past.

          2. helicopters do indeed require lots and lots of maintenance but somehow they manage to rotate them in and out of service using some sort of algorithm that you are apparently unaware of.

          3. All you guys talking about drones and blimps when you have a tether and need lift – what you need is a kite! Why use a hammer when you can use a rock to bang that nail in?

          4. Even plastic or other low observable materials would make for interesting RF characteristics of a rotary wing-mounted transceiver, and I’m not sure this “mount” could be held adequately steady, compared to a wire or mast mounted antenna.

            For better or worse, I serious doubt this system will be replaced. It was a fortuitous piece of hand-me-down from the vast infrastructure built to create a nuclear war fighting capability. Follow the money. The NSF and NASA spends ~US$79m/year with 3% annual increases to keep the Very Large Array going. For Arecibo, they spent US$8m in 2017, requesting $US6m for 2019. That suggests how much importance was given to keeping the lights on.

          5. “helicopters do indeed require lots and lots of maintenance but somehow they manage to rotate them in and out of service using some sort of algorithm that you are apparently unaware of.”

            And despite that some sort of algorithm that I’m apparently unaware of, you are apparently unaware that helicopters still manage to suffer mechanical failures and crash at a rate significantly higher than once in a half century.

          1. And one mild breeze, and there goes exposure. Finished.

            A fixed cable supported platform is the most stable and predictably reliable system still. It just needs to be boosted with 6 support towers, 4 for main support and 2 redundant support back ups. Cables offer the least amount of imaging interference, and with newer materials and methods, easier to maintain and design for long term strength and durability.

            What looks like concrete towers and metal cable retaining systems would have had a life failure time of about now given its age.

      1. I assume some of the weight is to avoid cable loss. So receiver preamps up there, maybe first conversion stages, so the signal into the cable to the receiver is stronger. In 1963 that would have required quite a bit of equipment. And given the weight, could the output stages for the transmitters be up there. this is sleculatiin, based on good practices, I’ve never seen details.

        The weight becomes a liability in the end, but perhaps it’s valuable for stability. You want the feed point to stay constant, weight limits issues of wind.

        I rewatched Goldeneye a couple of weeks ago, it’s all recognizable, , but it’s no guided tour.

      2. Next problem, is an electrically silent drone to put the RX/Instruments on. Then how do you get the info back to the lab? Laser? Maybe, but that needs power and has a weight penalty, so the size and weight of the drone bloats as a result. Oh, and how to power it for hours at a time? More weight (batteries etc.) Not practical at this time I think. But an interesting idea.

    1. Yeah, you can see in the drone footage just how many strands had already snapped.

      You can almost read the drone operators thoughts “Whelp, that cable looked pretty bad yesterday and that earthquake (in the Dominican Republic) this morning probably didn’t help, I’d better fire up the ol’ drone and take a look at the top of that tower…. “

    1. There had just been an earthquake in the Dominican Republic. Given the known, visibly bad state of the cables on that anchorage, they probably thought they better saddle up the drone and take a quick peek.

    2. Also, that tower anchorage had been the problem child, so it’ possible they were keeping an eye on it, detected strands snapping earlier in the morning and had gone up to investigate. You can see half a dozen strands are already broken in the moment before the first cable fails, which makes sense, often structural failures start slow and accelerate as the load transfers to fewer and fewer elements and the whole thing eventually “unzips”

      That brave third cable was able to hold out for couple of seconds, though. Good try, little cable, you gave it all you had.

    3. I had thought at first that it was lucky that the drone was looking at the one that snapped. Then I remembered that one had already lost two cables, so of course they would be looking at it. It was still a bit of luck that the drone was up when it happened. If, say, it had happened in the middle of the night, the drone wouldn’t have been up there.

  2. What a sad loss.
    I have no idea what could have saved it, but it probably would have survived longer had they had the maintenance budget required for such a device.
    We should build it again. (yes, I know that there’s no money for that.)

      1. Exactly. A needless, wasteful, negligent loss of taxpayer’s money maintaining massive steel structure well beyond its designed lifetime.

        We have more pressing issues than a couple of greybeards radiating EM energy into space. Major housing crisis for young generation, pointless jobs, lack of proper healthcare and COVID is the final blow to current “economy”. We should consider pursuing Chinese development model where their goal is not absolute economic growth for the few elites but harmonious society for everyone.

        1. 200M$ won’t make a dent in any of the problems you mention. Science however, can solve them all.

          If 200M would make a dent though, remember that that only amounts to the annual income of 20 lawyers. Do we really need /them/

        2. Oh bugger off with this. Aracibo was not some useless tool used by a bunch of “greybeards in ivory towers” to fritter away money on flights of fancy, it was one of the most powerful radio telescopes we had and was how we discovered our first Exoplanet, millisecond pulsar, binary pulsar, and FRB. If you want to argue the merits of maintaining such an aging facility fine, but you absolutely cannot argue from the perspective of “fundamental science is a waste of money.” Also, I wouldn’t exactly put China on the pedestal of “harmonious society”. You know, the country that continuously displays civil rights violations against Hong Kong and the Uyghur populations while implementing just short of thought police in their borders with their social media style “good citizen points” and Great Firewall.

  3. It looks like they had some sort of monitoring device attached to the top of the tower. It is the white box labelled WJE, which seems to be the logo of an engineering firm.

    This could have alerted them the cable was about to fail.

  4. In this video from Scott Manley has a bit of background information about the failure of the first cable. The first cable did not “break” (somewhere in the middle) but the end was pulled out of it’s socket.

    It also has some info of all the stuff inside the “Gegorian dome” and even without the rails system to move it, the mirrors in that dome would be far to big and heavy for some kind of drone to keep them positioned with mm accuracy.


    00:47 First cable. Look at the “square” end. It was pulled out of it’s socket.
    02:59 Photo of cable pulled out of socket.
    06:10 Iconic plot of pulsar data.
    07:30 Upgrade, fence on circumference.
    08:18 Upgrade, Gegorian dome and focus correction from the spherical dish.
    08:50 Instruments in Gegorian dome.
    10:25 Some nice radar images from Arecibo.

  5. I couldn’t watch to the end because I was furious that they wasted tax payers money on so many cables when one cable was enough all along!
    Hope they find out who decided to overbuild the thing.

    1. It’s worse than that, the one cable that was sufficient, was also holding up the weight of all the other redundant cables, so it could have been made much thinner! Typical big govt project overspend…

    2. Actually, it was a pretty good design.

      Back in August, one main cable broke. Thanks to structural redundancy the other 3 cables were able to carry the load, albeit in an ’emergency’ configuration.

      Had it been possible to replace the original cable expeditiously, we might still have a telescope.

  6. Can anyone here with experience in suspension/cable-stayed structure design/maintenance speak to the way the structure was built? I’m surprised by a couple things but I’m no expert. For instance, based on images taken during construction and during the failure, it looks like there was a whole lot of cable clamping going on — which seems like a weak design.

    Looks to me that the anchorages were built with cable stubs sticking out, support cables were clamped to those stubs and anchored to the towers, then main cables were anchored between the towers and the receiver frame.

    Suspension bridges typically have continuous cables that are wrapped around anchor points in the anchorages and are essentially “draped” over saddles at the tops of the towers.

    I can only assume that the design they chose is cheaper but I’m not quite seeing how.

    Anchorage construction: https://www.naic.edu/history_gal/jan191962.jpg
    Lofting receiver frame via initial cables: https://www.naic.edu/history_gal/sep141962.jpg

    1. The cable loads are quite different on either side of the tower because of the angles at which the cables meet the tower.

      The triangle platform needs about 300 tons of vertical lift on each corner. If the antenna-side cables make a 12 degree angle to the ground this means they are under a tension of about 1500 tons.*

      This cable pull toward the dish has a horizontal component of about 1400 tons, which can’t be provided by the rigid concrete towers so it must be resisted by the backstay cables. If the backstays rise at an angle of 60 degrees, then to generate 1400 tons of horizontal force they have to have a tension of about 2800 tons – about twice the tension on the antenna-side cables.

      The towers themselves are under about 2700 tons of compression, but they’re just big blocks of concrete that probably weigh ten times this on their own, so the load is almost incidental.

      It’s hard to tell just what is happening in the picture of the cable stubs coming out of the anchors, but it looks like they might be wrapped for protection, and whatever is under there is bulging out a bit at the ends. It’s possible that there is a proper cable end fitting under there.

      Also, you might want to look here for some cool information about building the dish


      ( * disclaimer – these are back-of-the-envelope numbers that come from looking at some pretty pictures of the before-times on the internet and ‘analyzing’ them with what I still remember from Statics 101. Mileage may vary with more accurate information )

      1. That’s some pretty good back-of-the-envelop math. The thing I was wondering about is, if we assume that the clamps are weak points (given that the failure occurred at one), if a continuous cable embedded in the anchorage then looped over the tower and run to the other towers would be significantly stronger? Doing this with three towers means you’d have to bind them near the center with something pretty tough so maybe it’s impractical without an even number of towers.

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