[LMB] Arecibo

Marc Wilson marc.wilson at gmx.co.uk
Mon Nov 23 20:53:34 GMT 2020

On Mon, 23 Nov 2020 20:26:27 +0100, Markus Baur via Lois-Bujold
<lois-bujold at lists.herald.co.uk> wrote:

>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
>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)

How about the L2 point?
The fact that an opinion has been widely held is no evidence whatever
that it is not utterly absurd;  indeed in view of the silliness of the majority
of mankind, a widespread belief is more likely to be foolish than sensible.
  - Bertrand Russell

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