Drone Footage of Arecibo Observatory Collapse

I noticed this too. Even though it was facing the wrong way, I think engineering classes will still find it valuable to dissect the first and second order effects on these cables over time

Can't help but think of post-Soviet installations in eastern Europe. Sometimes you can see empires literally falling apart.

This is what I'm wondering as well. Who is in charge of cleaning this up and restoring the gaping wound in this ecosystem?

You may know two people who have no use for Arecibo, but I know of many many more people who know the actual capabilities of Arecibo and know just how impactful the loss is, and that's just on the science side. The telescope also served as a gateway and source of inspiration for many young students in Puerto Rico. The Observatory ran many STEM related outreach programs over the years, with far reaching impacts.

The entire field of Planetary Astronomy has lost one of the best instruments for Earth-based observation of planetary objects in our solar system. Additionally, our capabilities for observing near-Earth asteroids has been been diminished, with Goldstone being the next most capable though it's sensitivity is nearly 20x lower than that of Arecibo.

FAST can perform some of the same science Arecibo can, but there's still a fair amount that can't. It's frequency range only goes up to 3GHz, which is only a third of what Arecibo's range was. Off-zenith, it's illumination area was only 25m in diameter larger (off-zenith it's beam was only 300m compared to Arecibo's 275m) so for most cases it's gain factor isn't substantially larger that Arecibo. Additionally, it's focal platform is much smaller, leading to less flexibility, though it's reduced frequency range does mean it needs fewer receivers to cover that range.

I think characterizing Arecibo as a microwave observatory is not correct. While AO did observe between 3 & 10GHz, that's only a tiny portion of the Microwave spectrum. AO's design was adequate for it's purpose, though clearly a newer redesign would make plenty of sense.

A white elephant it was not. It had modest budget needs compared to many other facilities. It's base operating costs was around 10 Million USD. For more serious maintenance efforts, it needed supplemental funds. However, it's been operating below that since NSF Astronomy started dialing back funding in the late 2000s.

NASA and NSF Atmospherics stepped in with additional funding as NSF Astro stepped back, but that still just met the operating costs and left little on the table for larger maintenance efforts.

Like many have said, the time for major maintenance was a decade ago, however, the funds weren't there, and neither was the knowledge that anything was wrong with the primary cables. All inspections performed showed no indication of major problems. We now know that the cables were not performing to the designed ratings, but hindsight is always 20/20.

I studied pulsars in University and worked with Arecibo, Green Bank, did some data analysis with VLA, and worked on some undergrad projects using low frequency arrays.

The details get complex, but the gist of it is that arrays let you see bright small scale things, while single aperture telescopes let you see large scale that are dim.

Additionally, an array suffers with sensitivity and noise issues if they don't have enough antennas covering discrete distance pairings. This usually occurs at short baselines since array elements often have a minimum spacing. Single aperture telescopes have a large instantaneous gain factor due to their large collecting area, which is really hard to make up without an exceedingly large number of array elements. For example, Arecibo has the same collecting area as ~148 VLA dishes.

Data handling for an array is complex as well, as you need to mix and process the data from each telescope to sync them together (correlation), while a single aperture telescope doesn't need this step.

On the other hand, an array is generally much less sensitive to instrument noise as the cumulative signal means noise from a single array element has a much lower impact overall. Also, it generally dodges the single-point failure modes by being essentially redundant. You can still operate with one or more elements missing/out of action.

Each telescope type has it's pros and cons, and there are equally valid use cases for each one.

One thing that I imagine is quite difficult to perform on an array is the type of planetary radar Arecibo specialized in by nature of it's high-power S-Band radar (2.38GHz). With AO's S-Band radar, it was possible to get highly detailed imaging and orbital parameters of near-Earth Asteroids with short observations, while determining orbital parameters with optical observations can take numerous observations (and doesn't generally give you the same detailed 3d models). NASA's Goldstone Observatory is the next best telescope for this, but is nearly 20x less sensitive due to it's size and different operating frequency.