archiv~1: Re: SETI Arecibo message to m13

Re: SETI Arecibo message to m13

Alfred A. Aburto Jr. ( (no email) )
Sun, 08 Nov 1998 15:28:32 -0800

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Subject: Re: SETI Arecibo message to m13
Date: Sat, 7 Nov 1998 12:51:04 +0000 (GMT)
From: David Woolley <david@djwhome.demon.co.uk>
To: aburto@cts.com
CC: nwelstead@seti.org.au, seti@sni.net, orbiter@tin.it,
astro@lists.mindspring.com

>> Al Aburto <aburto@cts.com> wrote:
>> But, if by some far out highly improbable accident, it
>> were detected it would cause any intelligent entity to be
>> curious because it is a complex message (not a tone but a
>> sequence of tones in a complex

> David Woolley <david@djwhome.demon.co.uk> writes:
> The signal would be detectable at a much lower
> sensitivity than needed to realise it wasn't a pure
> tone. The bin width might be as low as 0.1Hz and the
> integration time many hours.

Al Aburto <aburto@cts.com> writes:
The signal was transmitted at 12.6 cm wavelength (2.4 GHz).
The total power, including the Arecibo antenna directivity,
was 20 trillion watts! The data rate was 10 bits/sec. There
were a total of 1,679 bits (=> transmission time of 167.9
seconds (2.8 minutes)). It was transmitted as a string of
1's and 0's. Each bit had a duration of 0.1 seconds. It is
not clear what the bandwidth of the signal was unfortunately,
but an FFT of 0.1 seconds indicates a binwidth of 10Hz. It
was hoped that whomever (if anyone) received the signal they
would realize that 1,679 bits is the product of two prime
numbers (73 * 23 = 1679). They would then realize this may
represent a 2-D matrix of 73 rows by 23 columns. If then they
laid out the bit pattern as 73 rows by 23 columns they'd see
the picture (the one Nico showed in his last email
attachment).

The 2.8 minute message was only transmitted once. Averaging
longer than 2.8 minutes would be counter productive as it
would degrade the SNR.

> You would probably see the modulation side bands, but even
> if you re-analyzed the raw data after the initial detection,
> you might not get any more out of it. If the sidebands were
> distinct they might indicate an intelligent source but the
> short duration would probably make it difficult to rule out
> local interference.

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