A very interesting lecture. Thanks for posting the link!
One of the post-lecture questions asks "at what distance could we detect ourselves?". It appears the answer is only a few tens of light years. That's not quite what I was asking, but it gives the perspective I wanted. Practically, it seems we're very nearly blind.
Thanks for reading,
bob prohaska
Sam Harris is likely turning over in his grave.
Sam, W1FZJ, was famous for his VHF/UHF work. He was the East Coast half of the first 1296 MHz moonbounce.
He would build large arrays, such as square quad of 432 MHz yagis. Then he would build 3 more, ergo a quad of quads. He lived in New England and was famous for "If your antenna stays up all winter, it's not big enough...."
When he retired, it was to Puerto Rico. He was invited to come help at Arecibo. He looked at all the small things the million-dollar consultants didn't; such as coax connectors. The first 2 weeks he was there, he bettered their S/S+N figure by
2 dB.A toast to both him and Arecibo....
-- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close.......................... Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
Not exactly. They will probably exploit different laws of nature.
High power lasers weren't a plausible mode of interstellar communication when Arecibo started up.
Niven and Pournelle's "Mote in Gods Eye" speculates about that. Jerry Pournelle is a meat-head, but Larry Niven always did his homework. It wasn't intended as interstellar communication ... it was merely a side effect of launching an interstellar probe.
-- Bill Sloman, Sydney
A replay of the original signal would seems a good start.
Sadly it has just got a whole lot worse.
The feed gantry fell to the ground overnight smashing the big dish and it is now just a heap of rubble and twisted metal.
Dust still in the air in these recent Twitter images from the site.
and
A very sad end to major radio telescope.
-- Regards, Martin Brown
On a sunny day (Tue, 1 Dec 2020 16:56:36 +0000) it happened Martin Brown wrote in :
I have been wondering ever since they called it beyond repair if it would not be possible to (and I think that is all there is you need at the focus point) put the LNA (and cooling I presume) in a drone and have it hover using differential GPS in the exact position. I have tried that with my drone, powered by 100 kHz few hundred volt via thin coax indefinitely. Would not cost shit and can be setup in no time.
I really do not see the use of hanging a whole house over a dish. Accuracy with differential GPS is within some centimeters, but of course you could use lasers etc and even cameras for position control. Kids stuff. It is a nice dish, old brains there?
Well, it saved the NSF some money for controlled demolition. :(
Infrastructure maintenance is like saving for retirement: important but not urgent (until it's too late).
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
One thing that has puzzled me is why this is a thread in sci.electronics.design when sci.electronics.repair is right over there.
Might need some engineering repair, too, I guess.
Elijah
------ the bigger they are, the harder the fall
Arecibo workers seem rather lackadaisical about it all.
Why is nobody shouting 'incompetent gits'?
Was there no maintenance budget?
Didn't an alarm go off after the first stress failure?
RL
Yes, you do not see.
"the unique beam-steering mechanism suspended high above the reflector dish allowed for a moveable focal point that could aim at different parts of the sky."
It wouldn't be of much use with a fixed reflector to only look at the tiny portion of the sky it ends up being pointed at as the earth revolves and wobbles.
Sure, kid stuff! I can't imagine why no one has done it.
-- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
You do realize that dish is a *transmitter* too, right? How much transmitting power can your drone carry?
Also, depending on frequency, the transmitting/receiving antenna in the "house" might have a minimum size. How big is your drone again?
How much fuel does it take to hover a Sikorski Skycrane and payload in one spot for days on end?
It just broke.
-- John Larkin Highland Technology, Inc The best designs are necessarily accidental.
Frightening prospect to put 900 tons in the air suspended by cables then cut the funds needed for maintenance.
-- Science teaches us to trust. - sw
Scott Manley has a brief description:
Arecibo Radio Telescope Collapses!
Aricebo appeared in the movies:
GoldenEye - The Dish
(be prepared for some exaggeration)
-- Science teaches us to trust. - sw
The signal level for a radio telescope is so tiny that you need total radio quiet for some considerable distance around it. Any transmitter pointing into the dish would blind it. They even put mesh on parts of the ground to prevent the warm Earth from degrading the signal to noise.
I doubt your drone would be able to carry the feed cables or high power pulse transmitter and certainly not the secondary and tertiary reflectors.
It is a fair bit more complicated than it looks. That radome hides a lot of intricate equipment and a very high power pulse transmitter.
If you are interesting in more details search "arecibo egg frequencies".
Their website is denying me access but the google summary paragraphs contain most of the specifications of the instrument anyway.
It allows you to use the telescope for radar ranging. Almost all of the biggest dishes have something the size of a hut at the prime focus it allows the electronic engineers to work there without having to be professional mountaineers (although some of them are hobby mountaineers!). It is one hell of a long way down and a sheer drop!
They could operate at up to 8GHz you do the sums (3GHz was more common). The dish surface figure after its second face lift was good to 2mm.
I'm not sure how they compensated for wind loading and thermal cable stretch on the support gantry position but since it obviously worked they must have been able to do it. Lateral motion doesn't hurt so much.
-- Regards, Martin Brown
On a sunny day (Tue, 01 Dec 2020 16:24:40 -0500) it happened DJ Delorie wrote in :
Yes, transmitter, never thought about that, for sure you do not want to transmit trump's tweets to alien civilizations..
As to the carrying capability of modern drones, I think that is not much of a problem. The problem is more in the fact that the Arebico thing is a nineteenth century project. With a bit of tinkering and what we can do now, you could still make good use of that big dish. It can all be solved, nice student project: cost peanuts. Na sayers we do not need.
Power? we live in a world of green idiots where a 16 year old who likely cannot connect a light bulb misguides the world as a pawn in the game of the ever selling more windmills of your mind while we all know we need nuculear plants really.
;-(
But back to reality, nice student project, can be done. Get some traveling wave amplifier from ebay for a transmit test, Power is no problem, no RF communication if you have RFI fear, the 2.4 GHz modules can be swapped out simply you can go optical, bit of tinfoil has worked for many :-) Space if full of satellites that cover large part of the world with a little bit of solar power. Just DO it! Maybe there are political reasons to destroy Arebico? Seems to me they could have fixed those cables years ago?
Also, a while ago I was looking of optical power upload, and found some high power stuff (google).
It can all be solved.
'Merrica? I did read that China now also has a very nice big dish.
On a sunny day (Tue, 1 Dec 2020 13:06:09 -0800 (PST)) it happened Rick C wrote in :
That is EXACTLY what the drone gives you
nineteenth century thinking likely.
On a sunny day (Tue, 01 Dec 2020 15:57:35 -0500) it happened legg wrote in :
Good point! I did read they had 3 companies evaluate the structure,
2 said beyond repair. Majority rule and science... Politics and science do not always mix well.On a sunny day (Wed, 2 Dec 2020 09:19:04 +0000) it happened Martin Brown wrote in :
OK thank you, good info. But does not seem unsolveable to me with a drone. Sure in high windloads drone is likely out. But from an other POV if they just leave the thing as scrap metal now you have nothing. Drone is also safer for those poor techncians, 2 drones, one for backup.
Note the thin coax from the drone over the fence to ground control
At several hundred volt current is low and you can use the same coax for the signal too.
Crucially this means it can track an object as the Earth rotates whilst it pings radar pulses off its target.
Drift instruments have been built that can only observe objects as they transit the meridian or more restrictive still zenith.
Classical precision timekeeping started out that way at the Royal Greenwich Observatory. In radio astronomy the 4C Cambridge catalogue of radio sources was compiled by a drift instrument consisting of two parabolic trough reflectors forming an interferometer. The fixed one still survives although it is a bit threadbare now. Pictures are pretty.
OMT is far left, Half mile telescope in the distance (both on a *very* wide gauge railway track precisely running E-W and the remains of the parabolic skeleton of the former drift telescope is on the right.
Canada has a mercury mirror based optical drift scope in service today.
All the radio telescopes in the world are operated very close to the bleeding edge of what is technologically possible at the time. The deep sky network ones for communications with probes are more conservative.
-- Regards, Martin Brown
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