aericbo field of vison

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braunfeld

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Message 1160755 - Posted: 9 Oct 2011, 22:54:52 UTC

how much of the celestial sphere does arecibo see at any one point in time? we would like to know this as a percent of the celestial sphere.
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Message 1160772 - Posted: 10 Oct 2011, 0:02:03 UTC - in response to Message 1160755.  

how much of the celestial sphere does arecibo see at any one point in time? we would like to know this as a percent of the celestial sphere.

About 25% of the sky.
http://arxiv.org/pdf/1108.3134v2
page 2, 3rd paragraph from bottom

If you mean the beam width or the instantaneous amount of sky, for the Arecibo antenna at 2.4 GHz the beamwidth is about 0.028°. A very small percent.
http://en.wikipedia.org/wiki/Parabolic_antenna
It varies depending on where you have the feed horn and if you want to do the math ... http://www.naic.edu/~astro/aotms/performance/99-02.pdf

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Josef W. Segur
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Message 1160780 - Posted: 10 Oct 2011, 1:06:25 UTC - in response to Message 1160772.  
Last modified: 10 Oct 2011, 1:15:56 UTC

how much of the celestial sphere does arecibo see at any one point in time? we would like to know this as a percent of the celestial sphere.

About 25% of the sky.
http://arxiv.org/pdf/1108.3134v2
page 2, 3rd paragraph from bottom

It says "The survey thoroughly covers 25% of the sky (declinations from -2◦ to +38◦ )." However, calculating coverage from that declination range gives a figure of about 31% of the sky. It's not really a contradiction, the extremes of declination are not used except in very special circumstances.

If you mean the beam width or the instantaneous amount of sky, for the Arecibo antenna at 2.4 GHz the beamwidth is about 0.028°. A very small percent.
http://en.wikipedia.org/wiki/Parabolic_antenna
It varies depending on where you have the feed horn and if you want to do the math ... http://www.naic.edu/~astro/aotms/performance/99-02.pdf

The 3.4 arcmin HPBW of the LBW feed at 1420 MHz is actually fairly close to that for the ALFA feeds which are used for multibeam recordings, and the 2.5 MHz recorded bandwidth is centered at 1420 MHz. The applications base their calculations on 0.05 degree beam_width. Because there are 7 beams the instantaneous coverage works out quite close to 1 square degree, 1/41253 part of the full sphere, or 0.0024 percent.
                                                                 Joe
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braunfeld

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Message 1160800 - Posted: 10 Oct 2011, 2:29:58 UTC - in response to Message 1160772.  

so what is the percent of the total celestial sphere is it? i am wondering the following in my original post: if a signal was sent just once what would the probability of arecibo receiving the signal.
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Message 1160833 - Posted: 10 Oct 2011, 4:41:33 UTC - in response to Message 1160800.  

so what is the percent of the total celestial sphere is it? i am wondering the following in my original post: if a signal was sent just once what would the probability of arecibo receiving the signal.

Because the ALFA receiver system is only in use part time, divide the 0.0024% by about 6 to get 0.0004% probability the signal would appear in our recorded data. That assumes the signal is within the frequency range being recorded, of course.

According to the Science status page, the science database holds

Spikes     2,399,400,523
Gaussians    470,411,523
Pulses     1,152,742,122
Triplets   1,039,693,708


Any one of those could be a signal sent just once. However, multiple observations at different times (persistence) is needed to further reduce that amount of data so it's practical to consider more closely.
                                                               Joe
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Profile Bob DeWoody
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Message 1161159 - Posted: 11 Oct 2011, 6:35:51 UTC

No matter how you slice it the answer is not very much. at one time. But being near the equator and during a 24 hour spin of the earth a pretty good swath of the sky can be covered. But it beats not looking at all. A dedicated observatory on the far side of the moon would have a much better chance of finding ET, if ET is sending signals.

I still think we should be using the two voyagers to look back toward the sun and determine if their instruments are detecting anything unique in the noise that can be atributed to our being here and if so look for those signs elsewhere.
Bob DeWoody

My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events.
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Message 1161226 - Posted: 11 Oct 2011, 13:47:28 UTC - in response to Message 1161159.  

I still think we should be using the two voyagers to look back toward the sun and determine if their instruments are detecting anything unique in the noise that can be atributed to our being here and if so look for those signs elsewhere.

From their distance earth is now far far smaller than a single pixel.

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Profile Bob DeWoody
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Message 1161769 - Posted: 13 Oct 2011, 4:03:38 UTC

I understand that but I was wondering if they would be able to detect anything in the radio frequencies or in spectral analysis if aimed in the general direction of the earth and sun that would show as out of the ordinary.
Bob DeWoody

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Message 1161865 - Posted: 13 Oct 2011, 13:54:38 UTC - in response to Message 1161769.  

I understand that but I was wondering if they would be able to detect anything in the radio frequencies or in spectral analysis if aimed in the general direction of the earth and sun that would show as out of the ordinary.

You want to fly out to them and attach experiments they don't have? Okay.

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