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SETI Assumptions



>From: Steve Dimse <sdimse@telocity.com>
>On 12/23/00 3:54 PM Phil Karn (karn@ka9q.net) wrote:
>
> >This is exactly the algorithm the SETI folks use. They look for
> >doppler shifts represent the motion of the earth around the sun, and
> >the motion of the solar system relative to the rest of the galaxy.
> >This excludes a lot of terrestrial and earth satellite interference,
> >since they don't have the right doppler shifts.
> >
>Of course, if the aliens are as smart as we think, they won't be using 
>carriers, all their comms will be in spread spectrum, UWB, or something 
>even more efficient we haven't dreamed of!

Steve, Phil, and the bb:

I will keep this brief as I would guess this is "off-topic" for the
amsat-bb.   But I want to clarify some statements regarding SETI.  I'm a
four-year member of the SETI-League and regional coordinator for Alaska, so
know a "little" about the techniques used by both the "professional" radio
astronomers and us amateurs.

All SETI programs work from a set of assumptions {see Drake Eqsn}.  There
are two regarding possible signals from alien civilizations:
1.  They may be sending a beacon in attempt to make contact.  That leads to
looking for a narrow bw carrier-type signal for the obvious weak-signal
detection advantage.
2.  They have advanced space communications over long-range
{inter-planetary} and some of this may "leak" out over interstellar space.
Steve, your comments on modulation schemes are correct on this second
possibility.  BTW earth has been broadcasting since the 1930's enough
leakage RF to reach several nearby stars [~70 LY].

On the subject of doppler correction, I believe at least for amateur SETI,
that only earth rotational doppler is corrected.  But here I am not an
expert.  Best to contact Dan Fox author of the sw.

I won't comment any more about SETI on this list {thank you for your
patience this one time}.  Anyone wishing to comment or know more please use
direct e-mail or check into the public SETI list.  Details:  
http://www.setileague.org

Ed
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