Bad news from the world's largest usable aperture--Arecibo Observatory. https://www.nature.com/articles/d41586-020-02396-0
Photo by Phil Perrillat at AO. The bottom of the dish is shown here with the heating facility (incorporating antennas designed by WA3FET).
Had the pleasure of visiting the observatory in 2012. Take your time getting there... the roads are narrow and winding.
Photo of the broken cable. Spokesman said the cable was expected to have a 15-20 year remain life before requiring replacement. Failure investigation is underway. No estimate for repair cost or time frame. Comment: It appears to me that most of the cable elements failed suddenly [but I"m not a materials engineer]. Article with photos: https://www.space.com/arecibo-observatory-cable-failure-investigation.html
It's happened before ... "On September 21, 2017, high winds associated with Hurricane Maria caused the 430 MHz line feed to break and fall onto the primary dish, damaging about 30 out of 38,000 aluminum panels." * edit * oh, this latest looks much worse
Im surprised severe damage hadnt happened before in that hostile environment, that dish is getting rather elderly since it came alive in the early 60's. Many will probably remember Sam Harris, W1FZJ, of W1BU EME fame as the chief receiver engineer around 1965. Sam was one of my mentors when he still lived in MA. Carl
Maybe they can take advantage of the downtime and pressure-wash the reflector panels that weren't damaged. They were cleaned after Hurricane Maria three years ago, but in that climate the gunk doesn't take long to regerenate.
The 'gunk' has only very minor deleterious effects on the efficiency of the dish, whereas, trying to remove it will disrupt the position of the panels and lead to a costly 'realignment'. It looks crappy but has no practical effect on performance. Its not a negligence issue. Notice in the picture that the gunk is a very thin layer.
That wasn't a cable issue; parts of the feed broke off and caused major damage during the hurricane to the UHF feed in particular. THAT was expensive. While this picture (of the dish panels) looks pretty devastating, the damage was localized and WP3R says they will be up in a few weeks with repairs.
I am (or was before I retired) a materials physicist. Not quite the same thing as a materials engineer, but I had a couple of those working for me and I understood what they were talking about most of the time. I would not say for sure what the cause was, based on one photo, but IMO there's a high likelihood that it was either stress-corrosion cracking, or corrosion-fatigue. What it is not apparent in the photo and what will be important to know is where the cable broke - was it out in the middle somewhere -or was it at or near an attachment point ? That has a lot to do with the kind of stresses and environmental conditions that the cable was experiencing around the failure location.. A materials scientist/engineer will know pretty easily what the mechanism was via microscopic examination - i.e. corrosion-fatigue or stress-corrosion cracking. But the underlying cause, could be a lot more involved to figure out: i.e., was there a lack of inspection and maintenance, or was there pre-existing defect or damage, perhaps hidden from normal inspection and maintenance, or was there a short-cut or mistake made when it was installed, did the original contractor use the correct grade of wire or take a short-cut, even if there were stray currents / voltages could be important, and whether there was any electrochemical protection, coatings, etc, that may have degraded, was there more load on it than originally designed due to extra gear installed over the years?. Lots of things to consider. In the meantime, I assume they'll carefully inspect the other cables and attachments.
I found online some information about similar cable at Aricebo that was damaged in an earthquake in January 2014. That particular cable had a splice in it, because it was manufactured 12 feet too short ! ( I guess they never heard of "measure twice, cut once" ?) So they came up with a "splice box" and added another 12 feet to what they had. The earthquake-related failure occurred at the "splice box" *. And they contrived a "temporary repair" - but not clear to me if that "temporary" repair was ever replaced with a permanent repair. (The Planetary Society article) (Ammann & Whitney report) Interesting paragraph in the second link, above, the engineering firm says : "While the platform and towers would likely survive the complete failure of the cable we note that the cable falling from the tower would cause significant damage to the main reflector and any structures supporting the reflector ..." Deja Vu All Over Again? There's no indication at this point whether the recently failed cable was the same one that had been previously damaged. But I mention it because it shows that it's hard to know what really happened based on the information we have at this point (basically, one photo); there may be other, arcane, things involved that we can't even guess at this point.
Time to contact Synthetic Textiles for a full replacement package. If they can be used to hold an aircraft carrier they can produce something for that dish.
