So where's the science..?


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Profile Clyde C. Phillips, III
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Message 542820 - Posted: 8 Apr 2007, 18:51:32 UTC

I looked at the Wikipedia Allen Telescope reference. It looks like it will be sophisticated. However it still will only be one hectare while Arecibo is 7.3 hectares. Also it will cover several square degrees of sky, whereas Arecibo only looks at an area only three or four minutes (with the Alfa receiver) across. How could the sensitivity of Allen ever be able to approach that of Arecibo? One thing is that the Allen will be an interferometer. Maybe that'll narrow its field-of-view to something quite small. I don't know whether Allen could be as sensitive as Arecibo or not. Maybe it could be as Allen would looking at a truly small area if its dishes were spread out.
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Message 542851 - Posted: 8 Apr 2007, 20:29:58 UTC - in response to Message 542820.

I looked at the Wikipedia Allen Telescope reference. It looks like it will be sophisticated. However it still will only be one hectare...


I thought there were proposals to possibly turn it into a square kilometre array, would this be 'better' than Arecibo?
From Allen Telescope Array:
The astronomy decadal panel, Astronomy and Astrophysics in the New Millennium, endorsed SETI and recognized the ATA (then, the 1 Hectare Telescope) as an important stepping-stone to the Square Kilometer Array (SKA).

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Message 543072 - Posted: 9 Apr 2007, 9:05:07 UTC
Last modified: 9 Apr 2007, 9:07:09 UTC

MEN WANTED FOR HAZARDOUS JOURNEY. LOW WAGES, BITTER COLD, LONG HOURS OF COMPLETE DARKNESS. SAFE RETURN DOUBTFUL. HONOUR AND RECOGNITION IN EVENT OF SUCCESS.
Ernest Shackleton, Antarctic explorer (1874-1922)
(The advertisement above, placed in a London newspaper in 1912, inspired nearly 5,000 replies.)

Sounds a lot like the search by SETI@Home (just replace the word men with people)!!!
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Message 543170 - Posted: 9 Apr 2007, 15:07:29 UTC - in response to Message 542820.

How could the sensitivity of Allen ever be able to approach that of Arecibo?


See this picture:

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Profile Clyde C. Phillips, III
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Message 543245 - Posted: 9 Apr 2007, 17:45:37 UTC - in response to Message 542851.

I looked at the Wikipedia Allen Telescope reference. It looks like it will be sophisticated. However it still will only be one hectare...


I thought there were proposals to possibly turn it into a square kilometre array, would this be 'better' than Arecibo?
From Allen Telescope Array:
The astronomy decadal panel, Astronomy and Astrophysics in the New Millennium, endorsed SETI and recognized the ATA (then, the 1 Hectare Telescope) as an important stepping-stone to the Square Kilometer Array (SKA).


I heard that they were gonna put the Square Kilometer Array either in Argentina or in southern Africa. But if they turn the Allen Array into a square kilometer that will mean making 35,368 6-meter dishes instead of 354. How much would that cost, and would there be room for all those?

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Message 543249 - Posted: 9 Apr 2007, 17:53:06 UTC - in response to Message 543245.


I heard that they were gonna put the Square Kilometer Array either in Argentina or in southern Africa. But if they turn the Allen Array into a square kilometer that will mean making 35,368 6-meter dishes instead of 354. How much would that cost, and would there be room for all those?

I think the basic idea is that if you are going to make 350 of something, it's one price, and if you're going to make 35,000 then you can afford to set up a really good assembly line and get some economies of scale.

... and one thing I wonder about with the Allen Telescope: the original idea as I remember was to use "off the shelf" 3 meter "home satellite" dishes, which are (or at least were) mass-produced and quite inexpensive. Seems like the dishes at Hat Creek are all purpose-built.
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Message 543804 - Posted: 10 Apr 2007, 16:10:53 UTC

I just looked at the Allen Wikipedia reference and it looks like those reflectors are darn-well custom-built. Even the secondary probably has the wrong curvature for a (cut) three-meter run-of-the mill TV satellite dish, and it would be probably better to make all from scratch- all those supports, etc. But, yes, 35,000 would be far easier to make per dish than just 350. I would guess that those Allen dishes are far-better-built (surface accuracy, weather resistance, etc) than the 3-meter satellite dishes. Thats right - that means 35,000 steering mechanisms, too. Quite a project! How accurately would each dish have to be pointed in order to realize top potential?
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Message 543824 - Posted: 10 Apr 2007, 16:43:28 UTC - in response to Message 543804.

I just looked at the Allen Wikipedia reference and it looks like those reflectors are darn-well custom-built. Even the secondary probably has the wrong curvature for a (cut) three-meter run-of-the mill TV satellite dish, and it would be probably better to make all from scratch- all those supports, etc. But, yes, 35,000 would be far easier to make per dish than just 350. I would guess that those Allen dishes are far-better-built (surface accuracy, weather resistance, etc) than the 3-meter satellite dishes. Thats right - that means 35,000 steering mechanisms, too. Quite a project! How accurately would each dish have to be pointed in order to realize top potential?

I was thinking in the opposite direction:

If a crappy "home satellite" dish is only 50% effective, but at less than 10% of the (installed) cost of a fancy custom dish, it seems like you could double the number of dishes at 20% of the cost.

If you are optimizing per-dish performance, that's one thing. Optimizing performace per $$$ may be something else.

I'm sure smart people have looked at this and figured it out.
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Message 543925 - Posted: 10 Apr 2007, 23:40:23 UTC - in response to Message 543170.
Last modified: 10 Apr 2007, 23:40:58 UTC

How could the sensitivity of Allen ever be able to approach that of Arecibo?

See this picture:

Note that compares the Allen Array to Project Pheonix that ran at Arecibo. The sensitivity of the s@h analysis is greater.

Any comparisons anywhere?

Regards,
Martin

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Message 544277 - Posted: 11 Apr 2007, 15:01:24 UTC - in response to Message 508104.

Matt,

I hope you will remember, when planning the science analysis, to include the entire 2.5 MHz spectrum when looking for repeat signals from the same sky location. As I discussed with Dan a few years ago, a broadcast (rather than targeted-at-Earth) transmitter would have to be so powerful that the place to put it would be in close orbit around the local sun -- where it could grow large enough to collect significant solar energy without covering most of the real estate on the home planet or microwave-cooking everything on the planet.

This means that, due to the transmitter's orbital motion, the signal will have a modest rate of frequency drift but a large total frequency range -- which I think happens to be about 2.5 MHz for a transmitter orbiting a sunlike star at 0.1 a.u. (where solar energy is dense but not quite too hot for ordinary structural materials).

In fact I asked Dan if this was why he chose 2.5 MHz for the bandwidth, and I think he said no, it's a lucky coincidence.

Remember any transmitter we're actually going to hear has almost certainly been running for millions of years at least, so the aliens will have had ample time bu now to expand it to astronomical size and power, and this means it's likely to be in a near-star, fast orbit.

Alan MacRobert
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Message 544368 - Posted: 11 Apr 2007, 18:56:18 UTC

I don't even know what Project Phoenix was. At any rate it looks like the area of coverage of the Allen Array is/will be about 36x as great as Phoenix was. I measured the circles on my screen. However arent both circles really drawn too small? They cover only a small portion of a galaxy which may be only several minutes across. I believe that the Alfa receiver's field-of-view of each element is between three the four arcminutes across according to a drawing I saw. It's gonna take an awfully powerful signal to overcome all the noise in a circle over two degrees in diameter. But one is gonna have to be awfully lucky to have pointed a narrowbeam receiver in just the right direction. That means an awful number of workunits.
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Message 544619 - Posted: 12 Apr 2007, 2:08:10 UTC - in response to Message 544368.

I don't even know what Project Phoenix was. At any rate it looks like the area of coverage of the Allen Array is/will be about 36x as great as Phoenix was. I measured the circles on my screen. However arent both circles really drawn too small? They cover only a small portion of a galaxy which may be only several minutes across. […]

I believe those circles are intended to be interpreted as spheres representating ranges (for a given sensitivity threshold, I presume) rather than areas of coverage; they appear to be ‘embedded’ in the galactic disk rather than projected onto the celestial sphere. But of course no instrument that’s fixed to the Earth’s surface can see the whole sky unless it’s just about exactly on the Equator and capable of being pointed horizontally.

At any rate, if the diameter of the “Allen” sphere is six times that of the “Phoenix”, it encompasses 6^3 = 216 times as much space.

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Message 545295 - Posted: 13 Apr 2007, 3:20:01 UTC - in response to Message 544277.

Alan

Welcome back... It is nice that you keep up on what is happeing...

Matt,

I hope you will remember, when planning the science analysis, to include the entire 2.5 MHz spectrum when looking for repeat signals from the same sky location. As I discussed with Dan a few years ago, a broadcast (rather than targeted-at-Earth) transmitter would have to be so powerful that the place to put it would be in close orbit around the local sun -- where it could grow large enough to collect significant solar energy without covering most of the real estate on the home planet or microwave-cooking everything on the planet.

This means that, due to the transmitter's orbital motion, the signal will have a modest rate of frequency drift but a large total frequency range -- which I think happens to be about 2.5 MHz for a transmitter orbiting a sunlike star at 0.1 a.u. (where solar energy is dense but not quite too hot for ordinary structural materials).

In fact I asked Dan if this was why he chose 2.5 MHz for the bandwidth, and I think he said no, it's a lucky coincidence.

Remember any transmitter we're actually going to hear has almost certainly been running for millions of years at least, so the aliens will have had ample time bu now to expand it to astronomical size and power, and this means it's likely to be in a near-star, fast orbit.

Alan MacRobert
Senior Editor
Sky & Telescope


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Message 545418 - Posted: 13 Apr 2007, 11:25:02 UTC - in response to Message 545295.


Alan

Welcome back... It is nice that you keep up on what is happening...

Matt,

I hope you will remember, when planning the science analysis, to include the entire 2.5 MHz spectrum when looking for repeat signals from the same sky location. As I discussed with Dan a few years ago, a broadcast (rather than targeted-at-Earth) transmitter would have to be so powerful that the place to put it would be in close orbit around the local sun -- where it could grow large enough to collect significant solar energy without covering most of the real estate on the home planet or microwave-cooking everything on the planet.

This means that, due to the transmitter's orbital motion, the signal will have a modest rate of frequency drift but a large total frequency range -- which I think happens to be about 2.5 MHz for a transmitter orbiting a sunlike star at 0.1 a.u. (where solar energy is dense but not quite too hot for ordinary structural materials).

In fact I asked Dan if this was why he chose 2.5 MHz for the bandwidth, and I think he said no, it's a lucky coincidence.

Remember any transmitter we're actually going to hear has almost certainly been running for millions of years at least, so the aliens will have had ample time bu now to expand it to astronomical size and power, and this means it's likely to be in a near-star, fast orbit.

Alan MacRobert
Senior Editor
Sky & Telescope




Yes - Welcome Back Sir . . . it's been awhile eh? Posts by Alan M. MacRobert

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Message 553905 - Posted: 26 Apr 2007, 4:08:53 UTC - in response to Message 540271.

Thanks to Ned & Pappa on their responses. You are correct in your assumption that I do not know what's going on behind the scenes and what tools have been used across the project. I guess my point on open source was that it seems that the tool sets utilized to bring about the first phase of analysis for boinc & the seti client were developed by a wide group of individuals via open source effort. However, it seemed (probably incorrectly) based on Matt's comments above that the second phase of the science project to analyze the mass of results that have been received to date still needed a great deal of development effort to build the analysis tools, and that the development effort to date for that second phase was dependent upon development resources within the SETI science team. Based on Pappa's response it seems that more progress is being made in that area than meets they eye, but if not, allowing outside resources to help on the development of those analysis tools would enable the science to advise more rapidly.

If needed & someone was interested, is there a specific forum for helping out with that development effort?

Thanks!

The SETI science application is open-source, and a fair sized group of people is busy using that to make faster SETI science applications.

BOINC, both client and server, is open source, and there are volunteers actively helping with the development.

The BOINC server uses Apache, MySQL and the various servers at Berkeley are running either Solarus or Linux.

So, your point about open source was?


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Message 554156 - Posted: 26 Apr 2007, 13:00:07 UTC

New 'super-Earth' found in space

The new planet is not much bigger than the Earth
Astronomers have found the most Earth-like planet outside our Solar System to date, a world which could have water running on its surface.

The planet orbits the faint star Gliese 581, which is 20.5 light-years away in the constellation Libra.

any chance you guys can set a telescope looking at that star, well you never know?!? :)

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Message 554206 - Posted: 26 Apr 2007, 15:36:49 UTC

The differnece between S@H and Project Phoenix is that Phoenix is not an all encompassing survey taking in everystar it can get at a specific wavelength. Instead Phoenix surveys millions of channels between 1000MHz and 3000MHz. To do that they have to limit the searchlist. So they look at stars with known planets and stars that are believed to have stars, and they have a limit saying that it has to be withing 200 lightyears. That still leaves 1000 stars.

So theyr limitation and close "globe" to earth is intentionall and do not have anything to do with the comparable reception between Arecibo and the Allen.
Ie, it is like comparing apples and pears. They are not even getting close to the beginning of how far arecibo can actually listen. That is not their point.

Carl

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Message 554251 - Posted: 26 Apr 2007, 18:31:44 UTC

Interesting about Phoenix. Thanks.
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Message 554313 - Posted: 26 Apr 2007, 20:50:37 UTC

So they've found a class M planet around Gliese 581. Let's look at it a little closer.

1. It is about 14 times closer to its parent star than the Earth-Sun distance

2. It's year is 13 days long...

3. Has estimated temperatures between 0°C and 40°C so has the potential for liquid water on the surface.

4. Orbits a red dwarf.

Realistic chances for intelligent life are slim at best.

1. Being that close will cause massive tidal forces, both on the structure of the planet and on any liquid water on the planet.
- The massive tidal forces on the structure of the planet will result in a large number of volcanos and / or the planet being rotationally locked, that is there would be no day and night only a day side and a night side. Both these points would make it hard for intelligent life to evolve.
- If the planet is rotationally locked then it will not have a strong "earth" like magnetic field.

2. Any weather patterns will be ferocious due to the speed of the planets rotation around it's sun.

3. Being so close to any star will mean any solar activity will rain down on the planets surface due to potential not to have a magnetic field since it may be rotationally locked.

These small points alone point to an extremely slim chance of intelligent life having the ability to evolve.

Just my 2c worth.

Live long and BOINC.

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Message 554510 - Posted: 27 Apr 2007, 0:43:17 UTC - in response to Message 553905.

Tim

There have been many successes, part of that is in the Tech News Forum. It has explained a lot of the things that were silent, and if someone said something many would beat on them for no reason... You can look and see that the donations, hardware and cash are doing something! Yes some things take time for transition...

Astropulse Alpha is now running in Seti Beta... We hope to see Enhanced 5.18 "soon" which would allow MultiBeam to move to Seti Main...

So from an "Outsider" point of view as the higher powered servers get moved to the Server Closet and hooked to the Gigabyte Switch more things will improve...

There is still a machine that needs to be obtained for Near Time Persistency Checking... If I had to think about things that have been heard and completed since Nov 2006 I would have to do a couple of messages... A Large Portion of that history is in the Staff Blogg and the Tech News Forum... We jsut have to look...

The last six months has made Major Advancements!


Thanks to Ned & Pappa on their responses. You are correct in your assumption that I do not know what's going on behind the scenes and what tools have been used across the project. I guess my point on open source was that it seems that the tool sets utilized to bring about the first phase of analysis for boinc & the seti client were developed by a wide group of individuals via open source effort. However, it seemed (probably incorrectly) based on Matt's comments above that the second phase of the science project to analyze the mass of results that have been received to date still needed a great deal of development effort to build the analysis tools, and that the development effort to date for that second phase was dependent upon development resources within the SETI science team. Based on Pappa's response it seems that more progress is being made in that area than meets they eye, but if not, allowing outside resources to help on the development of those analysis tools would enable the science to advise more rapidly.

If needed & someone was interested, is there a specific forum for helping out with that development effort?

Thanks!

The SETI science application is open-source, and a fair sized group of people is busy using that to make faster SETI science applications.

BOINC, both client and server, is open source, and there are volunteers actively helping with the development.

The BOINC server uses Apache, MySQL and the various servers at Berkeley are running either Solarus or Linux.

So, your point about open source was?



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