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Arecibo Observatory Collapsed

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Re: Arecibo Observatory Collapsed

#291

Earlier quoted context omitted.

FAST cannot do radar astronomy, as it has no transmitting capability. Among other things, this means FAST is less useful for tracking near-earth asteroids.

I assume that due to the rotation of the earth that when Arecibo emits a radar beam that other radio-telescopes on earth collect? Otherwise only objects within Arecibo’s relatively narrow FoV (that are also very close to earth) would be detected - so wouldn’t a purpose-built (and steerable!) radar emitter be more useful?

Arecibo was steerable, that's what the receiver array was for.

Re: Arecibo Observatory Collapsed

#292
post #270

Earlier quoted context omitted.

Large portions of the towers fell. Large portions of the dish are destroyed. And if you're going to effectively build over again, you might as well build a bigger one.

Topography is a major determinant of the size.

Of course. And that is part of my point: Arecibo may not be the most sensible thing to rebuild if it's not salvageable and larger antennas exist.

Re: Arecibo Observatory Collapsed

#293

Earlier quoted context omitted.

There is no money for this. The National Science Foundation, the primary source of funding for Arecibo, has been trying to shut it down or offset its cost for years. NSF is a part of the US government, so it has been a victim of the cuts to public science that have affected universities and institutions across the US since the end of the Cold War and the Great Recession. You are right that it would be simple, but the…

>NSF victim of cuts to public science Why is this completely erroneous fact believed by so many people? Other than a 1 time injection due to the 2008 crisis, NSF funding increases nearly every year and is currently at its second highest budget ever: https://dellweb.bfa.nsf.gov/NSFRqstAppropHist/NSFRequestsand...

Thank you for the correction. I had been following the news about Arecibo mostly and had not investigated NSF's total funding.

Re: Arecibo Observatory Collapsed

#294

Earlier quoted context omitted.

FAST cannot do radar astronomy, as it has no transmitting capability. Among other things, this means FAST is less useful for tracking near-earth asteroids.

I assume that due to the rotation of the earth that when Arecibo emits a radar beam that other radio-telescopes on earth collect? Otherwise only objects within Arecibo’s relatively narrow FoV (that are also very close to earth) would be detected - so wouldn’t a purpose-built (and steerable!) radar emitter be more useful?

Nope, it transmitted and received. The range was limited to about Jupiter because the dish would move over the effective horizon before the signals returned.

Pretty incredible!

Re: Arecibo Observatory Collapsed

#295

Earlier quoted context omitted.

There is no money for this. The National Science Foundation, the primary source of funding for Arecibo, has been trying to shut it down or offset its cost for years. NSF is a part of the US government, so it has been a victim of the cuts to public science that have affected universities and institutions across the US since the end of the Cold War and the Great Recession. You are right that it would be simple, but the…

>NSF victim of cuts to public science Why is this completely erroneous fact believed by so many people? Other than a 1 time injection due to the 2008 crisis, NSF funding increases nearly every year and is currently at its second highest budget ever: https://dellweb.bfa.nsf.gov/NSFRqstAppropHist/NSFRequestsand...

The NSF budget increased dramatically between 1951-2008 -- but when accounting for inflation in the figures you linked, has declined by about 10% in real terms since then.

(That is, the 2010 NSF budget of $7.045 B in 2010 is in real terms equivalent to about $8.413 B today, about a billion dollars more than the real 2020 budget of $7.066 B, using the inflation calculator at [1].)

[1] https://www.in2013dollars.com

Re: Arecibo Observatory Collapsed

#296

Earlier quoted context omitted.

I assume that due to the rotation of the earth that when Arecibo emits a radar beam that other radio-telescopes on earth collect? Otherwise only objects within Arecibo’s relatively narrow FoV (that are also very close to earth) would be detected - so wouldn’t a purpose-built (and steerable!) radar emitter be more useful?

Arecibo was steerable, that's what the receiver array was for.

Sort of, 5 degrees isn’t exactly a lot.

Re: Arecibo Observatory Collapsed

#297

Earlier quoted context omitted.

Most radio astronomers would rather see the money spent on the SKA instead ( https://en.wikipedia.org/wiki/Square_Kilometre_Array ). Looking at the epoch of reionization is where the excitement is in low frequency radio astronomy these days. I know the SKA can't replace Arecibo's radar capabilities, but the SKA will do more interesting astronomy.

The U.S. is NOT one of the governments supporting the SKA.

Maybe now we can be?

Re: Arecibo Observatory Collapsed

#299
post #229

Earlier quoted context omitted.

> no way of replacing How did they build the cables in the first place? Couldn't they just snip the cables with a helicopter or unmanned drone with a flying chopsaw and string new ones as if it was a brand new construction? Basically I'm not understanding how it is impossible to replace something but it is evidently possible to build that something.

The dish is nothing but aluminum sheeting with holes in it. The vast majority of the cost and complexity are in the instrument cluster and the towers. There's not much of value left to repair at this point. As for replacing cables, anyone who has rebuilt a RAID array will tell you that hardware is most likely to fail when it's under stress, like when you have workers in the towers setting the footings for the new ult…

[deleted]

Re: Arecibo Observatory Collapsed

#300
post #238
post #229

Earlier quoted context omitted.

> no way of replacing How did they build the cables in the first place? Couldn't they just snip the cables with a helicopter or unmanned drone with a flying chopsaw and string new ones as if it was a brand new construction? Basically I'm not understanding how it is impossible to replace something but it is evidently possible to build that something.

Being unable to fix something you’re able to build isn’t unusual to anyone who has built a large and complicated structure. They had two different engineering firms look at it, and neither of them saw a safe path forward. It’s possible that repairing it was physically possible, but would have put people in harms way while they were, for example, detaching cables on an already unstable structure.

Also this video can help realize the amazing scale of this thing: https://youtube.com/watch?feature=emb_title&v=QZAWqk-wrzc

This was basically a whole building suspended into the air. Science or magic? Amazing engineering to be sure (but maybe not built with maintenance and security in mind)

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