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Far Out, going for hundreds of AU
Marcel
post Jul 18 2005, 01:46 PM
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Very interesting article (pdf).

http://astronauticsnow.com/mg_pubs/2005_Gr...4_IAA_Aosta.pdf

Also available as a "here" link on the 4th topic on

http://www.centauri-dreams.org/
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Bob Shaw
post Jul 18 2005, 02:17 PM
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Marcel:

Interesting - and the last paragraph speaks of a new DSN study of an 11m antenna 'Farm' concept for the downlink...

Bob Shaw


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Marcel
post Jul 18 2005, 02:25 PM
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Yeah, but that's the part i did not understand quite well i'm afraid. 11 m farm ? Do they mean a "farm" with 11 meter dishes in an array (like a Y-configuration) ? There are a lot of arrays MUCH bigger than that already.......aren't there ?

Marcel.
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djellison
post Jul 18 2005, 02:34 PM
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Lots of small dishes adding up to the same size as one large dish ends up as a cheaper option I presume?

Doug
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edstrick
post Jul 19 2005, 09:41 AM
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One of the "Purple Pigeons of Planetology" dream missions proposed post Viking, post-Voyager was "TAU"... Thousand Astronomical Units"... Hubble scale telescope and other instruments lobbed out of the solar system, maybe with a solar-electric propulsion system followed by Jupiter gravity assist <don't recall> on a 30 or 50 year mission.

Imagine the astrometry they could do in the galaxy with a 500 AU parallax baseline and hubble sized optics.
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AndyG
post Jul 19 2005, 11:58 AM
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QUOTE (edstrick @ Jul 19 2005, 09:41 AM)
Imagine the astrometry they could do in the galaxy with a 500 AU parallax baseline and hubble sized optics.
*

With a baseline that much bigger than Hipparcos' 2AU, the same resolving power, and a limiting magnitude six million times dimmer, we could be making 3d maps (including all M3V and brighter stars) across the galaxy to an accuracy of a couple of light hours... blink.gif

...be just about able to trigonometrically measure distances to stars as bright as Canopus in the Andromeda galaxy... ohmy.gif

Wow!

Andy G
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Bob Shaw
post Jul 19 2005, 03:32 PM
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QUOTE (djellison @ Jul 18 2005, 03:34 PM)
Lots of small dishes adding up to the same size as one large dish ends up as a cheaper option I presume?

Doug
*


Doug:

Basically, yes - albeit with certain caveats. You have much more data-handling, and perhaps even have to have cleverer engineering than a 'big ear' (I don't know about Arecibo, but Jodrell Bank's big dish has more in common with a railway bridge that moves (it's *HEAVY*) than a refined bit of hyper-engineered kit!). Nothing beats surface area, but the practicalities are such that a load off almost off-the-shelf devices with moderate engineering requirements can compete very well. But, you *don't* get something for nothing, though in an era of low-cost computation/GPS/laser surveying/high speed data links (to name but a few of the required technologies) you *can* get something very economically.

To put this in perspective, there's a company in Liverpool (I forget their name, an offshoot of one of the Universities, possibly John Moores) which is making a determined stab at 'production-line' research class optical telescopes, and if their financial model holds up we could see a lot of 'moderate' aperture optical work. Think of the value of a hundred 48" scopes with active optics compared to one or two biggies...

And, finally, remember that radio-telescopes actually *are* in mass-production and common use - there must be one on every other house, where I stay...

Bob Shaw


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tty
post Jul 19 2005, 05:06 PM
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QUOTE (Bob Shaw @ Jul 19 2005, 05:32 PM)
Doug:

And, finally, remember that radio-telescopes actually *are* in mass-production and common use - there must be one on every other house, where I stay...

Bob Shaw
*


Not to mention radar antennas. Radio astronomy very largely begun with surplus german "Würzburg Riese" antennas back in the late forties. Allied (especially english) radar antennas weren't built to tight enough tolerances to be useful, but german ones were.... rolleyes.gif

tty
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djellison
post Jul 19 2005, 06:06 PM
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I think that telescope company is in Birkenhead - didnt they make the mirrors for the Faulkes scopes? I remember going "Ohh - Birkenhead" because that's where Helen and I both herald from in our youth smile.gif
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Bob Shaw
post Jul 20 2005, 01:01 PM
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On the big radio telescope 'Railway Bridge' heavy engineering front, here are some pictures of Jodrell Bank which illustrate the scale of things. Some are in 3-D.
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Bob Shaw
post Jul 20 2005, 11:01 PM
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There *is* a reason for strong structures - as shown by the before and after shots of the 300' Green Bank dish (pics by Richard Porcas).

http://www.gb.nrao.edu/fgdocs/300ft/300foot.html
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ilbasso
post Jul 21 2005, 01:10 AM
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Man, I HATE it when that happens!


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Jonathan Ward
Manning the LCC at http://www.apollolaunchcontrol.com
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lyford
post Jul 21 2005, 01:42 AM
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QUOTE
The loss of the 300Foot telescope resulted in the Green Bank Telescope Project.

I think they did it on purpose so they could get this nice new shiny one... tongue.gif

Robert C. Byrd Green Bank Telescope

Hope no one was hurt....


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Lyford Rome
"Zis is not nuts, zis is super-nuts!" Mathematician Richard Courant on viewing an Orion test
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Bob Shaw
post Jul 21 2005, 08:52 AM
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QUOTE (lyford @ Jul 21 2005, 02:42 AM)
I think they did it on purpose so they could get this nice new shiny one... tongue.gif

Robert C. Byrd Green Bank Telescope

Hope no one was hurt....
*



Lyford:

You reckon it was an insurance job?

Hmmm... ...so that's the *real* conspiracy behind Mars Observer, Mars-96, MPL, MCO etc!

Bob Shaw


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lyford
post Jul 21 2005, 09:01 AM
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laugh.gif


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Lyford Rome
"Zis is not nuts, zis is super-nuts!" Mathematician Richard Courant on viewing an Orion test
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