[LMB] Arecibo

Markus Baur baur at chello.at
Mon Nov 23 19:26:27 GMT 2020


Am 23.11.2020 um 19:07 schrieb WalterStuartBushell:
>
>
>> On Nov 23, 2020, at 10:29 AM, Markus Baur via Lois-Bujold 
>> <lois-bujold at lists.herald.co.uk 
>> <mailto:lois-bujold at lists.herald.co.uk>> wrote:
>>
>> let us take the arecibo design as plubeprint and look where we can 
>> reduce mass
>>
>> the dish itself can be made from very lightweight aluminized foil (it 
>> does not have to deal with wind and rain) - this also means that the 
>> anchor cables for the dish can be made a lot thinner.
>>
>> we also might not make the cables (both for the dish and the gondola) 
>> from aluminium or steel - modern synthetics like Spectra offer a much 
>> better weight / strength ratio
>>
>> the receiver gondola suspended over the dish also does not have to 
>> deal with weather ..
>>
>> so i would not be surprised if it could be built with only 1/10 of 
>> the mass of the original
>>
>> total weight of the arecibo observatory seems to be around 1500 tons 
>> .. so a lunar arecibo would be around 150 tons
>>
>> and that is not completely out of bounds, if SpaceX gets the lunar 
>> version of the Starship to work (estimated paylaod to lunar surface 
>> aruond 40 tons .. 4 flights .. getting the resto of the necessary 
>> infrastructure (quarters for construction and maintenance crew, 
>> constructrion machinery, etc. ) up might take even more paylaod than 
>> the telescope itself
>>
>> servus
>>
>> markus
>>
>
> More feasible would put it in low Earth orbit, where there is 
> radiation protection from the Earth’s magnetic field,
> and it can scan more of the sky.

yes - it can scan a lot more of the sky .. but you also get  the full 
dose of earth's radio noise .. putting the telescope on the far side of 
the moon will cut down on the noise by an absolutely HUGE amount

also - it can look at one spot of the sky only at aa time .. but 
observations are planned a long time ahead - so having to wait 14 days 
to be able to see the "other side" of the sky usually is not a big burden

the long planning ahead also makes the 2 to 3 second communications 
delay from / to the far side not a big problem .. only if you absolutely 
need to hold a real time conversation, and even there 2-3 seconds are 
manageable

the logistics of building and maintainnig the telescope will be made 
easier in LEO yes ..

the radiation however will be a lesser problem - lunar regolith is a 
nice radio shield, but also a good radiation shield (the habitat for the 
building and maintenance crew will be below the surface)

servus

markus

> This give better logistics including retrieval of personnel and 
> significantly less
> lag time in communication.
>
> OBbj: Remember the time lag when Miles had his conversation with Dr. 
> Auditor Vorthys?
>
> Alternatively perhaps it could be located at L4 or L5, if we are OK 
> with remote operation and it
> could be assembled in low Earth orbit.
>> It is wrong, always, everywhere, and for everyone, to believe anything 
> upon insufficient evidence.”
> —W. K. Clifford (1845–1879), “The Ethics” My take is belief should be 
> proportional to the evidence.
>
>
>
>


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