|The default parameters above (frequency, dish
sizes, transmission power etc) are set to achieve a range of about 23 light
years which gives a little margin for Gliese 581 at a range of 20.4 light
years. Gliese 581 has 3 planets around it Gliese 581c and Gliese 581d are
both bordeline for being in the habitable zone, marginally too hot or too
cold, so there is a chance and it is worth studying this further. The
range is reasonable also at 20.4 light years, less then the default
communications link parameters above.
55 Cancri is
at a range of 41 light years.
The bandwidth is very limited, to about only 1 Hz, giving a transmission
bit rate of only 1 bit per second. This means that a single letter
might be transmitted every 8 seconds using ASCII code. If the
more efficient morse code was used then perhaps one letter every 3 seconds
might be possible. Please try higher bit rates, but notice that the
range reduces significantly unless you use bigger dishes.
You may speculate what coding method might be used and what format of
message might be sent. One idea is to send a picture comprising a
number of dots. Each dot is 1 bit, so provided the image is small it
does not take too long to send the complete image.
The image on the right is an example of what might be sent. It is
like a TV picture, made up of lines, each with 23 dots along each line.
The image is supposed to show some numbers, the DNA structure, a human
figure, the sun and planets and the SETI parabolic dish at Aricibo.
There are 69 lines, so in total there are 1587 bits to transmit, taking
about 26 minutes. If someone receives this signal then hopefully
they will detect that it repeats every 26 minutes. They will then work
out that the frame length is 1587 bits and realise that this is a multiple
of 23 x 69 and be able able to plot it out as a picture.
This message was actually transmitted on 16th Nov 1974 towards the M13
star cluster at a range of 25,000 light-years. I don't think there is any
hope of them receiving that distance. Even 21 light years is rather
I am interested to know if this page gives correct results. If you
agree or disagree please send details to me by e-mail
Copyright © 2002 Eric Johnston, All Rights Reserved.
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Most recent revision: 24 Oct 2007 ( One decimal point in calculation
Amended 7 Feb 2010
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Possible SETI message to send to the aliens on Gliese 581 !