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Arecibo observatory to be demolished


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At the time it was built, it was easier to do that sort of telescope vs interferometry. When the VLA was built, the integrator was fed by individually cut waveguides from each dish (changed with each configuration) so that the signals arrived at the same time lag from detection at each telescope's focus. Now things are far easier with time stamped data at the detector, and VLBI is a thing. It's far more sensible to build more capable arrays of smaller telescopes linked together than to fix Arecibo.

It was cool partially because of history, though, but I bet that repair costs are just grossly out of line with scientific return on investment.

Edited by tater
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*to be clear for anyone not getting the waveguide thing, the analog waveguides ran some extra length inside the building to make up for dish position so the signals had the same path length to the correlator room. The software dealt with most of it, but they wanted very precise path lengths as I recall so they knew how to deal with it. The correlator also dealt with the sky position of the source, which also changed path length as the Earth rotated.

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7 minutes ago, tater said:

At the time it was built, it was easier to do that sort of telescope vs interferometry. When the VLA was built, the integrator was fed by individually cut waveguides from each dish (changed with each configuration) so that the signals arrived at the same time lag from detection at each telescope's focus. Now things are far easier with time stamped data at the detector, and VLBI is a thing. It's far more sensible to build more capable arrays of smaller telescopes linked together than to fix Arecibo.

It was cool partially because of history, though, but I bet that repair costs are just grossly out of line with scientific return on investment.

Agree, added benefit of an array is that the array has larger aperture, wider arch of operation and you can divide it into multiple telescopes if you don't need the max performance. 
Now L3 is the obvious location for it 0 g is better than 1/6 g, still for radio I guess they go array here. Much larger aperture, L3 is pretty small after all :) and you can subdivide. 

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Ah well, I guess if two of the three-cable suspension system fails it'd have to be closed down for the time nevertheless.

 

We need a replacement, though - Arecibo was capable of transmitting radio waves, not just receiving them. While it was not very practical due to it only being able to use part of the whole dish at any given time, we should probably do something better.

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Well, it isn't all that surprising. The US (well, the NSF) have been trying to pull out of financing Arecibo since at least 2010 and only pressure and commitment from international partners have kept it alive so far. And with FAST being operational they even lost the bragging rights to having the biggest single dish. When I saw the pictures after the first cable snapped this year I was somewhat shocked how dirty the dish looked. While the dirt doesn't affect the operation as such, it is an indication that they are saving on maintenance. So, yes, sad but not surprised.

14 hours ago, tater said:

It's far more sensible to build more capable arrays of smaller telescopes linked together than to fix Arecibo.

Big single dishes and arrays of smaller telescopes have different applications. Yes, you can run an array in a "phased up" mode (in contrast to the normal interferometer mode) but the data is much more complicated to calibrate and even after calibration the data quality is just not the same. And doing things like absolute flux measurements or radar transmissions are next to impossible to do with an array.

 

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On 11/20/2020 at 6:52 PM, AHHans said:

And with FAST being operational they even lost the bragging rights to having the biggest single dish.

Still a loss of transmission capability. While using radar is now not that needed IMO you gotta have one somewhere...

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