End of an Era: Arecibo Observatory to be Demolished

[Palanan]

Deeply, deeply sad. The structure is literally falling apart.

I first learned about the Arecibo Observatory in the pages of Cosmos, and its appearance in Contact helped bring it to a wider audience. There may never be anything like it again.

[Tvtyrant]

Deeply, deeply sad. The structure is literally falling apart.

I first learned about the Arecibo Observatory in the pages of Cosmos, and its appearance in Contact helped bring it to a wider audience. There may never be anything like it again.

Hard to believe it can't be repaired, but they certainly know more than I do about it.

[hamishspence]

Deeply, deeply sad. The structure is literally falling apart.

I first learned about the Arecibo Observatory in the pages of Cosmos, and its appearance in Contact helped bring it to a wider audience. There may never be anything like it again.

It is sad. However, others have followed in the lead set by Arecibo.

https://en.wikipedia.org/wiki/Five-h...ical_Telescope

[DeTess]

Hard to believe it can't be repaired, but they certainly know more than I do about it.

As I understand it, two of the 6 cables one one of the three towers failed, with damage spotted to the other cables, meaning that we can't be sure how close they are to snapping as well. This means that the whole structure is now in a state where it could come down literally any second. Losing one more cable on that tower would put enough of a load on the remaining three that they'd be almost guaranteed to snap, even if they where in a fine and well-maintained state (which they aren't).

Any attempts to repair it would put even more strain on those cables, increasing the risk of collapse, and the people you'd have to send up there would be at a massive risk, because the structure could come down at any second. Even if you could bypass the risk of falling (using people suspended from helicopters or something like that), if one of these big cables snaps you do not want to be anywhere near it.

It's certainly sad, but I can understand the decision made to try and do a controlled demolishing of the structure, rather than waiting for chance. I do hope something similar would be rebuild afterwards, as the telescope was built because of a natural terrain feature that won't go away. given that this whole problem appeared because of budget issue with the agency in charge, I doubt there are any plans for a replacement.

[Radar]

All things come and go. What I find most sad about this news is that no one has apparently been doing regular check-ups on the structure and it lead to the current situation, where it is beyond repair. This is such a waste. At least there are newer telescopes to keep on listening to the song of the universe.

I remember ARECIBO most from the Goldeneye movie actually. I do not remember, if Cosmos series ever aired in my country to be honest.

[factotum]

As I understand it, two of the 6 cables one one of the three towers failed, with damage spotted to the other cables, meaning that we can't be sure how close they are to snapping as well.

In particular, the cable that snapped of its own accord did so while under a strain of only 300 tons or so, whereas they're supposed to be rated for 500 tons apiece--so clearly the structure is much weaker than it's supposed to be. You'd think they could just demolish the existing suspended structure and replace it with a smaller one, even if that removes the radar astronomy capability, but I guess they've costed that and decided it's just not worth it.

[Rogar Demonblud]

The Observatory was only built in the first place because Reagan thought it would work as an early warning system for the SDI anti-ballistic-missile system. Without that kind of blank check it was only a matter of time before it came down.

[Tvtyrant]

As I understand it, two of the 6 cables one one of the three towers failed, with damage spotted to the other cables, meaning that we can't be sure how close they are to snapping as well. This means that the whole structure is now in a state where it could come down literally any second. Losing one more cable on that tower would put enough of a load on the remaining three that they'd be almost guaranteed to snap, even if they where in a fine and well-maintained state (which they aren't).

Any attempts to repair it would put even more strain on those cables, increasing the risk of collapse, and the people you'd have to send up there would be at a massive risk, because the structure could come down at any second. Even if you could bypass the risk of falling (using people suspended from helicopters or something like that), if one of these big cables snaps you do not want to be anywhere near it.

It's certainly sad, but I can understand the decision made to try and do a controlled demolishing of the structure, rather than waiting for chance. I do hope something similar would be rebuild afterwards, as the telescope was built because of a natural terrain feature that won't go away. given that this whole problem appeared because of budget issue with the agency in charge, I doubt there are any plans for a replacement.

The whole thing is only 900 tons, there are cranes that could be installed to hold the entire platform up while they redo the cables. Considering oil platforms have been helicoptered into the jungle and assembled on site, it's not out of the engineering question.

The cost is probably though, and if the will to do it was there it would have been repaired before it got this bad.

[Xyril]

The whole thing is only 900 tons, there are cranes that could be installed to hold the entire platform up while they redo the cables. Considering oil platforms have been helicoptered into the jungle and assembled on site, it's not out of the engineering question.

Again, this might go to the issue of danger. I know that day to day operations for offshore oil platforms are almost an order of magnitude more dangerous than your typical job in the U.S., and that's just considered the cost of doing business. When you factor in the fact that we tend to be more tolerant of higher risk that's limited in scope (i.e., construction or installation), I wouldn't be surprised if the danger tolerance for bringing those inland oil platforms is substantially higher as well.

[Lord Torath]

I think I first heard about this telescope on 3-2-1 Contact on PBS.

I've heard that the NSF intends to maintain the site, and keep doing science/astronomy there. When the 100m dish in West Virginia collapsed in 1988, they replaced with with a fully-steerable replacement. That could be their plan for the Arecibo site (although I've heard nothing about that specifically).

[monomer]

The whole thing is only 900 tons, there are cranes that could be installed to hold the entire platform up while they redo the cables. Considering oil platforms have been helicoptered into the jungle and assembled on site, it's not out of the engineering question.

The cost is probably though, and if the will to do it was there it would have been repaired before it got this bad.

Remember that the farther out a crane has to reach, the less it can lift. The Arecibo dish is over 300m in diameter so the crane would have to be situated more than 150 m from the platform, say 160 m total to include room for the Crane itself. The sensor platform is also 150 m above the dish.

The largest semi-mobile crane in the world is the Sarens SGC-250 "Big Carl" which has a lifting capacity of 250,000 ton metres. That means at 160 m it has a 1558 tonne theoretical maximum, though with the fittings necessary for that extension it has a maximum load of 978 tonnes. At that point, though, it has a maximum height of about 85 m which probably isn't enough to reach the platform. Using the higher jib, it can reach 150m high at 160m extension, but then can only lift 662 tonnes.

So the world's largest crane can't actually do the job, and even if it could, there is only one of them and it took 250 trucks to move it to its current location in England where it will be for the next 4 years. Designing, building, and transporting a new one to Arecibo would be a huge engineering and financial challenge.

As for helicopters, the highest-weight heavy-lift helicopter is the MI-26 which can lift 44,000 lbs, or 22 short-tons. I don't think hovering over 40 helicopters in formation in a small area would be considered a safe prospect.

[factotum]

Designing, building, and transporting a new one to Arecibo would be a huge engineering and financial challenge.

And all that has to be done pretty darned quickly, because the structure is clearly not stable as it is now and could come down of its own accord at any time.

[Trafalgar]

It is sad. However, others have followed in the lead set by Arecibo.

https://en.wikipedia.org/wiki/Five-h...ical_Telescope

The whole thing is only 900 tons, there are cranes that could be installed to hold the entire platform up while they redo the cables. Considering oil platforms have been helicoptered into the jungle and assembled on site, it's not out of the engineering question.

The cost is probably though, and if the will to do it was there it would have been repaired before it got this bad.

The Chinese Five Hundred Meter Aperture Spherical Telescope (abbv. FAST) uses a "light weight feed cabin" though I cannot find an actual weight online. The 900 ton Arecibo receiver/feed cabin was built in the 60s when computers and electronics where almost infinitely larger than today. I understand Arecibo also has installed transmitters while FAST does not but I imagine a much smaller tranmitter can be built than whatever was installed in the 60s and 70s.

I wonder if the solution is to do a controlled demolition of the existing platform and installing a smaller one which will make maintenance easier. Maybe they can limit the damage to the dish some how.

[factotum]

The Chinese Five Hundred Meter Aperture Spherical Telescope (abbv. FAST) uses a "light weight feed cabin" though I cannot find an actual weight online.

It's about 30 tons, I believe, but it's considerably less powerful than Arecibo--for instance, it's not capable of sending out actual radar pulses over interplanetary distances like Arecibo could. I've already suggested they could replace the existing structure with a lighter one up-thread, but as I said there, you'd be facing a definite loss of functionality doing that.

[Trafalgar]

It's about 30 tons, I believe, but it's considerably less powerful than Arecibo--for instance, it's not capable of sending out actual radar pulses over interplanetary distances like Arecibo could. I've already suggested they could replace the existing structure with a lighter one up-thread, but as I said there, you'd be facing a definite loss of functionality doing that.

I am pretty sure that radar technology has greatly advanced since the 1960s and a much smaller transmitter is now possible. I think the biggest problem is getting adequate power to the transmitter. According to this website, the current transmitter at Arecibo takes 1 Megawatt of power. AWACS aircraft have radar transmitters maybe 1/10 that (hard to find the wattage of military radar) so I think it is possible to come up with a lower weight transmitter than what was installed in the 60s, 70s, 80s, 90s. I think the main problem will be the size of the wire cross section to carry the Megawatt of electricity to the platform. That cross section size is unaffected by Moore's Law and is hard to get around, barring an advance in superconductors.

But, Moore's Law could mean that a 1 MW transmitter is no longer needed. Increased computer power might mean that several images of the object can be simultaneously compared, creating a higher resolution with a weaker transmitter than a single image from a higher power transmitter.

I think that a more powerful, renewed Arecibo is possible but NSF is perpetually strapped for cash and that kind of fix would take support from a divided U.S. Congress.

[factotum]

I am pretty sure that radar technology has greatly advanced since the 1960s and a much smaller transmitter is now possible.

Well, the obvious question then becomes, why didn't the Chinese do that for FAST? Because they definitely did not.

[Rogar Demonblud]

Too be blunt, there are things you don't share with countries you've had shooting wars with in living memory.

[Lord Torath]

The wider your lens - or mirror, in this case - the fainter the signal you can detect, and the better the definition you can get. This is a truth that holds for all telescopes. That's the main reason astronomers and astrophysicists like to build them big. Doesn't matter how much radar technology has improved, the bigger dish lets you detect fainter signals.

[Trafalgar]

Well, the obvious question then becomes, why didn't the Chinese do that for FAST? Because they definitely did not.

At the end of the day, radar is limited by distance no matter how powerful the transmitter is. If you send the signal out and it returns when the dish is on the far side of the planet, you don't detect anything. I am not sure what the range on Arecibo's Radar is but I can't find any examples of it doing anything past Saturn.

So if the Chinese Government isn't interested in, say asteroid topography, there might have been no benefit to working through this problem. Or mounting a radar transmitter may have taken away from another capability. I think one mistake we make in the west is assuming anything China builds is a copy of something we have. FAST has capabilities that Arecibo never had that are probably more useful than radar.

All I am saying is in the 21st century you don't need a 900 ton platform to have a radar along with everything else. If FAST's platform is 30 tons, I imagine you can have a radar at 40 tons.

[Xyril]

I am pretty sure that radar technology has greatly advanced since the 1960s and a much smaller transmitter is now possible. I think the biggest problem is getting adequate power to the transmitter. According to this website, the current transmitter at Arecibo takes 1 Megawatt of power. AWACS aircraft have radar transmitters maybe 1/10 that (hard to find the wattage of military radar) so I think it is possible to come up with a lower weight transmitter than what was installed in the 60s, 70s, 80s, 90s. I think the main problem will be the size of the wire cross section to carry the Megawatt of electricity to the platform. That cross section size is unaffected by Moore's Law and is hard to get around, barring an advance in superconductors.

Moore's law also doesn't affect the antenna geometry. While you can probably compensate for lower antenna gain by pumping more power through the transmitter, I imagine there are other relevant antenna parameters that are harder to achieve at smaller sizes and more difficult to work around. (It's been years since I took antenna and receiver theory, so my memory of this isn't the best, sorry.)

Another important consideration is that improvements in phased antenna array design have made it possible replicate much of the functionality of large antennas like Arecibo at a fraction of the cost. They can't duplicate all functions, which is why the efforts to preserve Arecibo have been motivated by more than historical sentiment, but they do enough (with the potential to do more as the field matures and computational power improves) that they're a very tempting alternative to cash-strapped institutions.

[Sermil]

Another important consideration is that improvements in phased antenna array design have made it possible replicate much of the functionality of large antennas like Arecibo at a fraction of the cost. They can't duplicate all functions, which is why the efforts to preserve Arecibo have been motivated by more than historical sentiment, but they do enough (with the potential to do more as the field matures and computational power improves) that they're a very tempting alternative to cash-strapped institutions.

Another important consideration is whether radio astronomy is going to get the most science per dollar right now. If I had a bucket of astronomy money, I would probably being putting into gravitational wave detectors that could improve the resolution of our current (LIGO/VIRGO) systems. It feels like big-fixed-dish radio astronomy is not a huge advancement over a few decades ago; we're not going to see that much new stuff. Meanwhile, phased array radio astronomy and gravitational-wave astronomy are growing by leaps and bounds. A new gravitational-wave observatory could show so many new facets of the universe. Even if it just had the sensitivity of the current Advanced-LIGO system, a new system somewhere far away from the others would significantly improve our ability to get directional information. And, of course, fast-tracking one of the space-based, mega/gigameter arm observatories (LISA, DECIGO, etc) would be incredible.

TL;DR We have finite science money, and while Arecibo was great, I wonder if there are better uses for that money than repairing it.

[Arcane_Secrets]

It collapsed today before it could be demolished.

https://www.cbsnews.com/news/arecibo...ico-collapses/

I'd call it deeply symbolic, actually.

[DeTess]

Here's a quick explanation on youtube about the sequence of events of the collapse: https://www.youtube.com/watch?v=vchDbyIRP44

The short version seems to be that a very minor earthquake caused a third cable on the tower that had already lost two cables to break, after which everything came down.

[factotum]

It collapsed today before it could be demolished.

https://www.cbsnews.com/news/arecibo...ico-collapses/

I'd call it deeply symbolic, actually.

BBC article has an overhead view of the remains--pretty clear that the only way to recover from *that* would be a total rebuild:

https://www.bbc.co.uk/news/world-us-canada-55147973

Goes to show just how dangerous the structure was, though, imagine if they'd decided to repair it and there were workmen on it at the time this happened? Doesn't bear thinking about.

[Tvtyrant]

They made the right decision there, for sure.

[Yora]

Shouldn't be any trouble to get a modern replacement for it before the James Webb Telescope is launched.

[Gnoman]

Shouldn't be any trouble to get a modern replacement for it before the James Webb Telescope is launched.

Probably the opposite. The James Webb Telscope won't be sucking up huge amounts of money after launch, so there's a pretty solid chance that rebuilding Arecibo will be possible with that money.

[Radar]

They made the right decision there, for sure.

Well, the much needed repairs were as it seems neglected for many years most likely due to lack of budget for it. In a sense this is just the final step of a long degradation process. In the last months there was indeed nothing that could be done, since maintenance work should have been done years ago.

[Lord Torath]

Video of the collapse has been released: Bad Astronomy.

There's a view from one of the buildings on the ground, and another from a drone that was right at one of the towers when the cable let go.

[factotum]

Interesting, so somebody must have been on site inspecting that tower with the drone when the collapse happened, and they still had the presence of mind to turn the drone around to view the aftermath--whoever that is has serious guts.