The investigation into why a cable mysteriously broke on the Arecibo Observatory has begun 9

[WKTaylor]

I have seen flight control cable failures under high tensile load... especially during crashes... but nothing like this failure...

Failure obviously occurred under high tensile load... wire strands unwinding/splaying about... but the break appears almost straight across all the wires at one discrete location. This is going to be an interesting failure analysis...

The investigation into why a cable mysteriously broke on the Arecibo Observatory has begun
Officials at the Arecibo Observatory in Puerto Rico still don't know what caused a cable failure that severely damaged the facility's iconic radio telescope this week, forcing it to shut down temporarily.

On Monday (Aug. 10), an auxiliary cable supporting a platform that is suspended above the 1,000-foot-wide (300 meters) radio dish broke and crashed into the telescope's reflector panels, creating a gash in the dish measuring about 100 feet (30 m) long.
… …

https://www.space.com/arecibo-observatory-cable-failure-investigation.html

From the article... A photo of the support cable that broke on Aug. 10, 2020. (Image credit: University of Central Florida)


Regards, Wil Taylor
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[Comcokid]

The location of the Arecibo antenna in Puerto Rico is ideal. The #1 issue is to have a radio-free zone, and that part of Puerto Rico has been designated as such since the early 60's and the ocean to the south is not subject to encroaching urban development (a problem with Green Bank Observatory in West Virginia). Arecibo is built into a natural karst valley of nearly a spherical shape which allows for it's large size.

Puerto Rico is a humid environment but is still less stressful than a hot/cold/freezing environment with addition issues of occasional snow ice buildup. I don't know if such environmental factors played a part in the collapse of the big dish at Green Bank in 1988 (

https://public.nrao.edu/gallery/the-collapsed-300foot-telescope/

). Note this antenna was 300 ft diameter. Arecibo is/was 305 meters . Green Bank had this 300 ft dish replace with a smaller 140 ft dish. Green Bank became independently funded in 2016 as NSF pushed to get if off their books.

The Atacama Large Millimeter Array (ALMA) in the high desert of Chile at an altitude 16,000 ft (5,000 m) is located there for other reasons. Arecibo operates up to 10 GHz. ALMA operates at 31 to 1000 GHz, a frequency band heavily attenuated by water vapor. The location in Chile allows it to get above much of the water vapor in the atmosphere. Like the big optical telescopes on the peaks of Mauna Kea Hawaii there are serious logistics issues at these altitudes. You have to pass a high-altitude physical to work there. Rooms are pumped with extra oxygen. Stays are limited to only a few days before you have to return to a lower elevation. You locate an observatory at these altitudes only if the science requires it.