APOD: Arecibo Telescope Collapse (2020 Dec 09)

[JohnD]

You may believe that, I couldn't possibly comment!

[RJN]

The videographers have now been identified and their names added to the Credits on the main NASA APOD. Thanks for those who pointed this out! - RJN

[neufer]

I wish one or more of America's billionaires would contribute their money to rebuild it. I'm specifically looking at you Bill Gates, Jeff Bezos, Elon Musk, and Laurene Powell Jobs. Warren Buffet too, but I don't think he's much into high tech pursuits. It would amount to pocket change for all of them.

I wish one or more of America's billionaires would contribute their money to a fully steerable radio telescope or interferometer.

Composite image of a spectral line observation of star forming region W51, showing the distribution of ammonia in the region. The image of the telescope from a time lapse film of a night of observations

---

<<The Robert C. Byrd Green Bank Telescope (GBT) in Green Bank, West Virginia, US is the world's largest fully steerable radio telescope. The Green Bank Telescope operates at meter to millimeter wavelengths. Its 100-meter diameter collecting area, unblocked aperture, and good surface accuracy provide superb sensitivity across the telescope's full 0.1–116 GHz operating range. The GBT is fully steerable, and 85 percent of the local celestial hemisphere is accessible. It is used for astronomy about 6500 hours every year, with 2000–3000 hours per year going to high-frequency science. Part of the scientific strength of the GBT is its flexibility and ease of use, allowing for rapid response to new scientific ideas. It is scheduled dynamically to match project needs to the available weather. The GBT is also readily reconfigured with new and experimental hardware. The high-sensitivity mapping capability of the GBT makes it a vital complement to the Atacama Large Millimeter Array, the Expanded Very Large Array, the Very Long Baseline Array, and other high-angular resolution interferometers. Facilities of the Green Bank Observatory are also used for other scientific research, for many programs in education and public outreach, and for training students and teachers.

In response to limited budgetary issues, the Division of Astronomical Sciences (AST) of the National Science Foundation (NSF) commissioned a portfolio review committee, which conducted its work between September 2011 and August 2012. The committee, which reviewed all AST-supported facilities and activities, was composed of 17 external scientists and chaired by Daniel Eisenstein of Harvard University. As part of the committee's August 2012 recommendation for the closure of six facilities, was that the Robert C. Byrd Green Bank Telescope (GBT) should be defunded over a five-year period.

In July 2014, the United States Senate Committee on Appropriations approved the NSF's fiscal year 2014 budget, which did not call for divestment of the GBT in that fiscal year. The facility then began looking for partners to help fund its $10 million annual operating costs.

On October 1, 2016, the National Radio Astronomy Observatory at Green Bank separated from the NSF and began accepting funding from private sources to stay operational as an independent institution, the Green Bank Observatory.>>

[Cousin Ricky]

How was this allowed to happen??
I don't understand the political position of Puerto Rico, it's a 'territory' (not a state) of the US! But part of the US, not some poverty-stricken third world country! And the US allows a prime astronomy instrument to fall apart? What???

You speak as if the USA isn’t already a third world country, coasting on past glory, run by politicians who hold science in disdain, who in turn were elected by two generations of voters raised by their religious leaders to distrust secular education.

The Arecibo Observatory simply has not been valued over the years by those with the purse strings.

[Cousin Ricky]

Dollars to doughnuts that it was hidden corrosion that did it in. A tropical, humid climate is hell on machines and maintenance must be diligent.

Some suspect the swarm of earthquakes 50 km to the south at the beginning of this year may have contributed.

[FLPhotoCatcher]

Click to play embedded YouTube video.

The "guilty party" is years of underfunding by different agencies. This instrument has been a target for defunding and decommission for many years. It's been limping along on borrowed time for a long time now. The catastrophic failure likely just accelerated what was going to happen anyway, for reasons having nothing to do with its physical condition.

The catastrophic presidency likely just accelerated what was going to happen anyway.

Trump accelerated the collapse?

No, I don't see how people can blame Trump for the collapse.

[neufer]

Dollars to doughnuts that it was hidden corrosion that did it in.

A tropical, humid climate is hell on machines and maintenance must be diligent.

• A tropical, humid climate full of thunderstorms is not ideal for radio astronomy either.

Some suspect the swarm of earthquakes 50 km to the south at the beginning of this year may have contributed.

Figure 1: Vertical exaggeration is 5:1.

---

Figure 4

---

The Tectonic Setting and Geology of Puerto Rico and Its Surrounding Seafloor
By Michael Cheadle - University of Wyoming

Figure 1. Bathymetry of the northeast corner of the Caribbean Plate showing the major faults and plate boundaries; view looking south-west. The main bathymetric features of this area include: the Lesser Antilles volcanic arc; the old inactive volcanic arc of the Greater Antilles (Virgin Islands, Puerto Rico, and Hispaniola); the Muertos Trough; and the Puerto Rico Trench formed at the plate boundary zone between the Caribbean and obliquely subducting North American Plates.

Puerto Rico is bounded on the south by the Muertos Trough, on the west by the Mona Canyon, and on the east by the Virgin Islands Basin (Figure 1). The Muertos Trough is an elongated basin developed where the Earth’s crust to the south of Puerto Rico is thrust under the Muertos fold-and-thrust belt, which lies to the south of the island. Mona Canyon (Figure 4) is an approximately north-south trending canyon which is almost 30 kilometers across, formed by east-west rifting.

The epicenter of the 1918 San Fermin magnitude 7.5 earthquake is located just to the north of the Canyon and the earthquake was likely caused by faulting related to this rifting. This earthquake triggered a six-meter high tsunami wave that swept along the west coast of Puerto Rico and may have generated the large landslide shown in Figure 4.

Lastly, the Virgin Islands Basin is an extensional basin which lies at the south-western end of the Anegada Trough, a feature that was explored in 2013 and 2014 by the E/V Nautilus. Together the Muertos Trough, the Mona Canyon, the Virgin Islands Basin/Anegada Trough, and the Puerto Rico Trench, define the margins of the Puerto Rico-Virgin Islands microplate, a small coherent block trapped between the larger Caribbean and North American plates.

[Cousin Ricky]

Lastly, the Virgin Islands Basin is an extensional basin which lies at the south-western end of the Anegada Trough, a feature that was explored in 2013 and 2014 by the E/V Nautilus. Together the Muertos Trough, the Mona Canyon, the Virgin Islands Basin/Anegada Trough, and the Puerto Rico Trench, define the margins of the Puerto Rico-Virgin Islands microplate, a small coherent block trapped between the larger Caribbean and North American plates.

So, what you’re saying is that we in Puerto Rico and the Virgin Islands (except St. Croix) are stuck between a rock and a hard place.

[neufer]

So, what you’re saying is that we in Puerto Rico and the Virgin Islands (except St. Croix) are stuck between a rock and a hard place.

A trough and a trench.

Scylla and Charybdis

http://asterisk.apod.com/viewtopic.php? ... 32#p308817

[Chris Peterson]

No, I don't see how people can blame Trump for the collapse.

"Blame" is probably not the right word. But it is easy enough to recognize that an administration that valued science might have resulted in different funding decisions among various agencies which might have expedited repairs before the failure became unrecoverable.

Trump may not be to blame, but his anti-science policies sure didn't help things!

[neufer]

Notional view of LCRT on the far-side of the Moon.

---

Concept of operations for building LCRT.

---

Lunar Crater Radio Telescope (LCRT) on the Far-Side of the Moon
Saptarshi Bandyopadhyay, NASA Jet Propulsion Laboratory

<<An ultra-long-wavelength radio telescope on the far-side of the Moon has tremendous advantages compared to Earth-based and Earth-orbiting telescopes, including:

• (i) Such a telescope can observe the universe at wavelengths greater than 10m (i.e., frequencies below 30MHz), which are reflected by the Earth's ionosphere and are hitherto largely unexplored by humans, and
  
  (ii) the Moon acts as a physical shield that isolates the lunar-surface telescope from radio interferences/noises from Earth-based sources, ionosphere, Earth-orbiting satellites, and Sun’s radio-noise during the lunar night.

We propose to deploy a 1km-diameter wire-mesh using wallclimbing DuAxel robots in a 3-5km-diameter lunar crater on the far-side, with suitable depth-to-diameter ratio, to form a sphericalcap reflector. This Lunar Crater Radio Telescope (LCRT), with 1km diameter, will be the largest filled-aperture radio telescope in the Solar System! LCRT could enable tremendous scientific discoveries in the field of cosmology by observing the early universe in the 10– 50m wavelength band (i.e., 6–30MHz frequency band), which has not been explored by humans till-date.>>

[JohnD]

What a good idea! But while rust might not be the same problem it was at Arecibo, there will be one or two additional maintenance costs.

[neufer]

What a good idea!

But while rust might not be the same problem it was at Arecibo, there will be one or two additional maintenance costs.

First, however, they should send up a lunar satellite with 6 perpendicular radio antennae sticking out
and then use the rising & setting of radio sources over the lunar horizon to spatially resolve the sky.

(Temporal resolution of known pulsars could be achieved using their already known periodicities.)

[Chris Peterson]

What a good idea!

But while rust might not be the same problem it was at Arecibo, there will be one or two additional maintenance costs.

First, however, they should send up a lunar satellite with 6 perpendicular radio antennae sticking out
and then use the rising & setting of radio sources over the lunar horizon to spatially resolve the sky.

(Temporal resolution of known pulsars could be achieved using their already known periodicities.)

Gaia has already done that to a much higher resolution than is possible with a single radio telescope. And it's a lot easier to work with an optical model of the sky than a radio one. And lunar satellites are always short-lived.

[neufer]

Click to play embedded YouTube video.

.
Gaia makes 3-D sky maps in the visible.

I'm talking about a 2-D sky map in radio waves of decameter wavelength or longer.

What a good idea!

First, however, they should send up a lunar satellite with 6 perpendicular radio antennae sticking out
and then use the rising & setting of radio sources over the lunar horizon to spatially resolve the sky.

(Temporal resolution of known pulsars could be achieved using their already known periodicities.)

Gaia has already done that to a much higher resolution than is possible with a single radio telescope. And it's a lot easier to work with an optical model of the sky than a radio one.

[Chris Peterson]

Click to play embedded YouTube video.

.
Gaia makes 3-D sky maps in the visible.

I'm talking about a 2-D sky map in radio waves of decameter wavelength or longer.

First, however, they should send up a lunar satellite with 6 perpendicular radio antennae sticking out
and then use the rising & setting of radio sources over the lunar horizon to spatially resolve the sky.

(Temporal resolution of known pulsars could be achieved using their already known periodicities.)

Gaia has already done that to a much higher resolution than is possible with a single radio telescope. And it's a lot easier to work with an optical model of the sky than a radio one.

Not arguing against radio telescopes. Just suggesting that there is not much value in a small one orbiting the Moon, and certainly not for the purpose of spatially resolving the sky.

[neufer]

Not arguing against radio telescopes.

Just suggesting that there is not much value in a small one orbiting the Moon,
and certainly not for the purpose of spatially resolving the sky.

• A small lunar satellite could easily have hectometer long antennae
  and resolve the sky using the Moon, itself, for (hourly) occultations.

<<Early radio astronomers found occultations of radio sources by the Moon valuable for determining their exact positions, because the long wavelength of radio waves limited the resolution available through direct observation. This was crucial for the unambiguous identification of the radio source 3C 273 with the optical quasar and its jet, and a fundamental prerequisite for Maarten Schmidt's discovery of the cosmological nature of quasars.>>

It would certainly be more cost effective than a lunar surface based radio telescope.

[Chris Peterson]

Not arguing against radio telescopes.

Just suggesting that there is not much value in a small one orbiting the Moon,
and certainly not for the purpose of spatially resolving the sky.

• A small lunar satellite could easily have hectometer long antennae
  and resolve the sky using the Moon, itself, for (hourly) occultations.

<<Early radio astronomers found occultations of radio sources by the Moon valuable for determining their exact positions, because the long wavelength of radio waves limited the resolution available through direct observation. This was crucial for the unambiguous identification of the radio source 3C 273 with the optical quasar and its jet, and a fundamental prerequisite for Maarten Schmidt's discovery of the cosmological nature of quasars.>>

It would certainly be more cost effective than a lunar surface based radio telescope.

I guess I don't understand goal you have in mind for this instrument.

[neufer]

I guess I don't understand goal you have in mind for this instrument.

• A UHF, VHF, HF or even LF Band All Sky Survey.

<<The C-Band All Sky Survey (C-BASS) is a radio astronomy project that aims to map the entire sky in the C Band (5 GHz). It has been conducted on two radio telescopes, one operating in the Karoo in South Africa, the other at Owens Valley Radio Observatory in California.

The survey has mapped not only the intensity but also the orientation of the incoming electromagnetic waves (polarization) at every point on the sky with an angular resolution of 0.73 degrees. The angular resolution represents the smallest details that can be distinguished in the images. This has been the first survey to map the sky at a frequency of 5 GHz—low enough to be synchrotron radiation dominated but high enough to be relatively unaffected by Faraday rotation. At this frequency most of the signal comes from emissions from high-energy electrons spiraling around magnetic fields in the galaxy. This radiation is highly polarized and a major foreground distorting the Cosmic Microwave Background (CMB) signal.

The primary scientific goal of the project is to aid in the subtraction of foreground radiation, mainly from our own galaxy, from measurements of the CMB in order to improve the exactness of the CMB measurements. The CMB is polarized, this polarization can help shed light on inflation theory and gravity waves in the early universe. Secondary goals include studying the magnetic fields within the Milky Way, the WMAP Haze and spinning dust.>>

[Chris Peterson]

I guess I don't understand goal you have in mind for this instrument.

• A UHF, VHF, HF or even LF Band All Sky Survey.

<<The C-Band All Sky Survey (C-BASS) is a radio astronomy project that aims to map the entire sky in the C Band (5 GHz). It has been conducted on two radio telescopes, one operating in the Karoo in South Africa, the other at Owens Valley Radio Observatory in California.

The survey has mapped not only the intensity but also the orientation of the incoming electromagnetic waves (polarization) at every point on the sky with an angular resolution of 0.73 degrees. The angular resolution represents the smallest details that can be distinguished in the images. This has been the first survey to map the sky at a frequency of 5 GHz—low enough to be synchrotron radiation dominated but high enough to be relatively unaffected by Faraday rotation. At this frequency most of the signal comes from emissions from high-energy electrons spiraling around magnetic fields in the galaxy. This radiation is highly polarized and a major foreground distorting the Cosmic Microwave Background (CMB) signal.

The primary scientific goal of the project is to aid in the subtraction of foreground radiation, mainly from our own galaxy, from measurements of the CMB in order to improve the exactness of the CMB measurements. The CMB is polarized, this polarization can help shed light on inflation theory and gravity waves in the early universe. Secondary goals include studying the magnetic fields within the Milky Way, the WMAP Haze and spinning dust.>>

Okay. But it isn't clear to me that an orbital radio telescope of the sort you're describing would be much help for this. You can get aperture, but with such a tiny collection area that I wonder if anything new would be detected.

[JohnD]

Raising this subject again, because through a webpage from the Royal Institution ( https://royalsociety.org/blog/2022/03/dish-of-the-day/ ) I've come across a video analysis of the engineering aspects of the collapse. The conclusion seems to be that by the time that the deterioration of the telescope was understood, it was so unsafe that there was no way to repair it without endangering the work force! The camera drone was up at the top of the suspension tower when it came down because the staff could HEAR strands breaking in the cables!

The presenter discusses the 'safety factor' in the original construction, the ratio between predicted load and strength of the components, and concludes that the Arecibo's factor was 2 when, say, a suspension bridge's cables would the three times stronger than predicted load, and the cable of a lift (elevator) have a factor of ELEVEN. It's remarkable that the Arecibo lasted so long!

See: https://www.youtube.com/watch?v=3oBCtTv6yOw

JOhn