Decommissioning of Arecibo Observatory’s 305-meter telescope

WBahn

Joined Mar 31, 2012
26,398
I expect to see small sections of the dish panels for sale on the Internet as commemorative souvenirs soon.

And some of them might even have been somewhere near Arecibo at some point.
 

andrewmm

Joined Feb 25, 2011
884
Wonder why all the tops of the three towers collapsed ?
Would one going , bring down the others ?

Anyway ,its stops any discussion about further use ,
like optical telescopes, just because there is Hubble does not mean the other ground base scopes are irrelevant,
Its been coming a long time, but
the more means we have to do science the better,
so its a great loss ,
 

Thread Starter

nsaspook

Joined Aug 27, 2009
7,862
Wonder why all the tops of the three towers collapsed ?
Would one going , bring down the others ?

Anyway ,its stops any discussion about further use ,
like optical telescopes, just because there is Hubble does not mean the other ground base scopes are irrelevant,
Its been coming a long time, bu
the more means we have to do science the better,
so its a great loss ,
I suspect it happen much like this.
The towers are in compression tension with balanced forces from the wire anchors to the weight of each leg of the lifted deck.
the-radio-antenna-platform-of-the-arecibo-observatory-in-puerto-rico-as-well-as-three-support-...jpg
When one of the three sides snap, the anchor forces will likely snap that one backward. The deck would swing down pulling the tops of the other two towers off as the deck crashes offset to that side..
 

WBahn

Joined Mar 31, 2012
26,398
Imagine that you are standing on a tree stump wearing a harness that has a ring on the front connected to two springs pulling in opposite directions, left and right, each with a tension of, say, ten thousand pounds. You don't feel anything because the loads balance themselves. What is going to happen if the spring on the left detaches itself? Yep, you go sailing off to the right.

You can see from where the cab slammed into the side that the support opposite the point of impact failed and then the cab swung down on the remaining supports. The cab was something like 900 tons and the load on the cables was many times that because of the angles involved. Those cables were trying to pull the tops of the towers inward and there's no way the towers themselves could support that kind of load (especially with that much of a moment arm) so there were guy cables pulling the tops of the towers outward to balance the force. When the load in the cables supporting the cab released, the guy cables were now unbalanced and that was way too much load for the towers to support so they all snapped at the top most joint. It looks like the top part of the towers were basically flung back into the surroundings by the guy lines.
 

WBahn

Joined Mar 31, 2012
26,398
You can see that what happened to the towers is exactly what we described. As soon as the load from the cab was removed, the supporting wires because a huge unbalanced load that snapped the towers before the cab even hit the ground.
 

andrewmm

Joined Feb 25, 2011
884
WOW,

Thanks for the video , I guessed there would be one, but did not find it,.

As is said above, looks like the failing cable decided to let go, then the centre swung down, held by the other two cables, and as the lateral force was to great for the two remaining towers, they snapped.

Good job the top of the towers were designed to fail first, else the towers in their entirety would have come down,

A Very sad day,
always wanted to go there,
was offered a trip back 30 years ago, but decided not now, now its gone.

I gather the encroaching population ( all with micro wave ovens and old cars ) has diminished what it could do, but the under investment is a serious shame.

As it was built for the cold war, it will never be re made, and its Radar capability was fairly unique I understand.
lets hope the Chinese share their scope,
 

Thread Starter

nsaspook

Joined Aug 27, 2009
7,862
WOW,

Thanks for the video , I guessed there would be one, but did not find it,.

As is said above, looks like the failing cable decided to let go, then the centre swung down, held by the other two cables, and as the lateral force was to great for the two remaining towers, they snapped.

Good job the top of the towers were designed to fail first, else the towers in their entirety would have come down,

A Very sad day,
always wanted to go there,
was offered a trip back 30 years ago, but decided not now, now its gone.

I gather the encroaching population ( all with micro wave ovens and old cars ) has diminished what it could do, but the under investment is a serious shame.

As it was built for the cold war, it will never be re made, and its Radar capability was fairly unique I understand.
lets hope the Chinese share their scope,
Unfortunately technical structures like Arecibo were not designed to be repaired at the major structural level while in a finished state after long periods of high static tension on cables and support towers. Level the site and rebuild a new radar that will last for another 60 years.

https://spacenews.com/nsf-says-its-too-early-to-decide-whether-to-replace-arecibo/
With repair no longer an option, the debate now turns to whether the radio telescope should be rebuilt. At the briefing, NSF’s Gaume said it was too soon to evaluate if the telescope will be rebuilt.

“With regards to replacement, NSF has a very well-defined process for funding and constructing large-scale infrastructure, including telescopes,” he said. “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.”

One aspect of that scientific assessment is the astrophysics decadal survey. The latest survey, dubbed Astro2020, is ongoing, and expected to be completed in the spring of 2021. Gaume didn’t comment on any impacts the collapse of Arecibo will have on Astro2020. Rob Margetta, an NSF spokesman, said after the briefing that NSF notified the Astro2020 steering committee of the collapse but has not made any requests for the committee to evaluate the impact of the loss of the telescope.
 

Thread Starter

nsaspook

Joined Aug 27, 2009
7,862
What's the annualized cost of that... plus the mainantance and operation I wonder? I'm surprised we don't have a better more efficient way to do this today like the arrays.
Don't know how much but we can easily handle the cost over that time period. We do have better methods today that can also be used to make a new single large dish more capable than the original.
 

schmitt trigger

Joined Jul 12, 2010
364
@WBahn
Excellent analysis.
There are videos of an ultra high antenna tower failure (North Dakota, I believe) where one of the guy wires failed and the tower was pulled on the opposite direction by the tension of the remaining guy wires.
 

andrewmm

Joined Feb 25, 2011
884
Re a better way,

There is no substitute for real size.
a large dish almost noiselessly concentrated the signal,
so if the dish gave even say 6dB gain, then an equivalent array listening would have to have as a first level approximation, a 6dB quieter receiver.

Yes I know, with processing, and averaging, multiple arrays can "null" out the "noise" , but it does have an effect on the signal.
Now for transmission, yes phased arrays allow much better power / beam shape,
but for receive, bigger is better.

Ok, china has a bigger one now, but
you never hear a scientific site say , hay we have spare time we don't know what to do with ...

IMHO, the site has been under developed for decades,
The multiple cables were up to be replaced many times, one at a time.
acoustic monitors were due to be installed on the cables to monitor there status,
but it was put off for "another year" ..

The facility is a great loss to the world.
 

Thread Starter

nsaspook

Joined Aug 27, 2009
7,862
IMHO, the site has been under developed for decades,
The multiple cables were up to be replaced many times, one at a time.
acoustic monitors were due to be installed on the cables to monitor there status,
but it was put off for "another year" ..

The facility is a great loss to the world.
I'm a believer that maintenance engineers are not fools and what many people see as lack of maintenance is more like, don't open that can of worms unless it's absolutely needed because the actual repair cost to like new condition of old worn equipment will only increase exponentially with deep inspection. They knew the real repair cost would be massive for even a one bad cable job because the others would likely need replacement too during a detailed tear-down inspection/repair sequence.

They did an inspection in 2014 after a major earthquake, the cable(s) believed damaged were repaired. I'd be shocked they didn't know at this point the other leg cables were also compromised.
https://www.prnewswire.com/news-rel...-repaired-following-earthquake-249837941.html
MENLO PARK, Calif., March 12, 2014 /PRNewswire/ -- On January 13, 2014, the William E. Gordon radio telescope in Arecibo, Puerto Rico sustained damage following a 6.4 magnitude earthquake that was centered 37 miles northwest of Arecibo. Following the earthquake, Arecibo Observatory staff conducted a structural survey that revealed serious damage to a main suspension cable section, with apparent breach of several cable strands within that cable, which supports the 900-ton focal platform of the telescope. There are 18 main suspension cables in all.

A short cable segment and splice near the top of one of the telescope towers, which is more rigid than the rest of the suspension system, suffered damage when the earthquake shook Arecibo. Ammann and Whitney Consulting Engineers were brought in to assess the damage and to consider repairs needed before the telescope could return to full operations.

"In an abundance of caution, telescope motion had been very limited since the earthquake," said Robert Kerr, Ph.D., the Observatory's director and a principal scientist at SRI International, which leads a multi-organization team that manages, operates, and maintains the Arecibo Observatory. "Nevertheless, the telescope continued its science mission, including participation in a 10-day global ionospheric study in late January and continuing a productive search for pulsars in the sky above Arecibo."

Arecibo Observatory has now completed the immediate repair of the William E. Gordon telescope. The repair design was created by Ammann and Whitney and the structural repair work was performed by Arecibo Observatory staff. Beginning on March 13, the telescope is back to full service for the scientific community.
https://www.planetary.org/articles/0409-arecibo-observatory-earthquake-repairs
Hanging in the high-humidity environment of Puerto Rico for over 50 years is one thing, and getting damaged by a magnitude 6.4 earthquake is another, but this cable in particular was already in a bad way: when the observatory was constructed in the 1960s, this cable arrived too short. The end was encased in zinc and spliced to another cable section, making this portion of the structure relatively rigid. When the earthquake hit, the cable began to unravel.

Years later.

https://govtribe.com/opportunity/fe...e-suspension-cable-replacement-ucf598#details
Federal Contract Opportunity for Arecibo Observatory Main Telescope Suspension Cable Replacement UCF-598. The NAICS Category is 5413 - Architectural, Engineering, and Related Services. Posted Jun 22, 2020. Due Jul 20, 2020. Posted by the Division of Acquisition and Cooperative Support (NSF). The work will be performed at Arecibo, 00612, Puerto Rico
Our Summary
The University of Central Florida (UCF) is seeking a contractor to replace one of the main telescope suspension cables at the Arecibo Facility located in Puerto Rico. The project consists of the replacement of a 3” diameter stranded cable (M8-4) of roughly 700-foot length, and it is one of nine cables on the Arecibo telescope. Responses to the Invitation for Bid (IFB), are requested by the Bid Due Date and Time indicated on UCF’s Public Purchasing Website located at https://ucf.bonfirehub.com/opportunities/28696. For additional information please contact Eddie Nieves by email at eddie.nieves@ucf.edu or telephone at 787-878-2612.
Before the aux or main cable broke.

https://fp.ucf.edu/wp-content/uploads/vendors/advertisements/AreciboCable/ITB_Cable Replacement 6-23.pdf
One of the auxiliary cables that helps support a metal platform in place above the Arecibo Observatory in Puerto Rico, broke on Monday (Aug. 10) causing a 100-foot-long gash on the telescope’s reflector dish. Operations at the UCF-managed observatory are stopped until repairs can be made.
After the AUX cable broke. The dish was doomed at this point.

http://spaceref.com/news/viewpr.html?pid=56582
The firms have been working around the clock since Nov. 6. A monitoring team has been closely watching all the cables and platform. Drones and remote cameras are being used to minimize risk.

Preliminary analysis indicates the main cable, which failed on Nov. 6, should have easily handled the extra load based on design capacity. Engineers suspect it is likely that the second cable failed because it has degraded over time and has been carrying extra load since August. A final determination could not be made without retrieving and analyzing the second cable.

The engineering firms cannot verify the integrity of the other cables at this time supporting the 900-ton platform. Each of the structure’s remaining cables is now supporting more weight than before, increasing the likelihood of another cable failure, which would likely result in the collapse of the entire structure.
After the first main cable broke.

The remaining main cables seem to have concealed internal rot that was the death blow to the dish.
 

andrewmm

Joined Feb 25, 2011
884
You mention the maintenance / service engineers,
I would never say anything against them,
Its as ever Snr management that control the pennies,

A sad sad loss to the world,
 

Thread Starter

nsaspook

Joined Aug 27, 2009
7,862
You mention the maintenance / service engineers,
I would never say anything against them,
Its as ever Snr management that control the pennies,

A sad sad loss to the world,
Unfortunately sometimes the only way to get funding from Sr. Management is to let it all fall down.

5047b0744fc37c149edcb26cd700dacd--property-management-humor-golf-quotes.jpg
 
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