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SIM SETI images from Contact IX

This exercise involved the simulated reception and translation of an alien radio signal.

Human Team's Personal Comments

Signal Characteristics

With a four day timeline, where's what we know about the signal,
as prompted by your questions, which I relayed to the ETs; repsonses
*slightly* paraphrased:

1) using a 4 microradian resolution, we can detect no parallax
shift. Let's arbitrarily assume the most favorable viewing angle (that
is, the initial detection is happening when the earth's motion is
perpendicular to the line-of-sight to Alpha Centauri). Assuming that the
earth moves 10^7 km in four days, the signal appears to be coming from a
distance of at least 2.5 * 10^12 km, which is 3 light-months.

2) We cannot see any angular separation between the source and
Alpha Centauri -- they both lie on the same line-of-sight, at our
present resolution.

3) Doppler shifts: over four days, we are not seeing significant
doppler shift other than that produced by the earth's rotation about its
axis. In other words, so far as doppler shifts go, the source appears to
be stationary (or moving at a constant velocity) with respect to the

4) The "beam" is circularly polarized. The polarization is not
modulated. All the information is being conveyed as tri-state (on, off
and null) frequency modulation. Beep and boop stuff. Real
straightforward. No gimmicks, there.

5) In other parts of the radio spectrum around this carrier, we
don't see any information-carrying signals, but periodically, a strong
carrier slowly sweeps across the spectrum towards the frequency the
"beam" is being transmitted on.

6) There is no periodicity in our reception; the source
looks to be active and on a line-of-sight with earth all the time.

7) Yvan Dutil wrote:
"I think we could detect ET's planet now. Using CFHT
with adaptive optic we could have a resolution of 0.1"
in infrared. A planet at the same distance as the earth
as the sun will be at 1" from the center of the system.
Infrared light is the best for this kind of observation
because the contrast is best at this wavelenght. Using a
narrow band filter center on absorption line of the sun
and stellar coronograph we could detect this planet. It
will be tricky need a lot of of time but we couls do this
Now. The mesurment of the wooble of Alpha Centauri have
been made since a lot of time. But, it's need also a lot of
time to make a good mesure. By exemple, if Centauran observe
the wooble of sun to find Jupiter they would need 20 year
for comfirm there discovery because they need to orbital
period minimum to be sure to not make an error."

RESPONSE: [I won't even paraphrase]
On a meta-meta level, I am not sure that even using a narrow
band filter, he can really detect an earth-sized planet over
the "noise" of the star, but it's arguable, so let's say he
can, with 0.1 arc-sec resolution. In that case, he does find
that Alpha Centauri-A has planetlike bodies. He finds nothing
closer than 0.2 arcsec nor further than 3 arcsec from AC-A. He
does not see anything like a disk of dust nor an asteroid belt
at any distance. He does find a body at 0.9 arcsec from AC-A.
In the infrared, it looks like small (nonJovian) nonluminous
body; there is nothing unusual about its appearance in the
infrared; it looks like one of the inner planets in the earth's
solar system.

8) re the "it's too simple" point raised by David Boulton:
a) content: The ETs are intentionally sending a simple message
b) form (beeps converting to graphs): ditto
c) conventions (X-Y coordinates, math tables etc): META> the
ETs decided to aim for something we could reasonably hope to decode.
The assumption is that a real SETI would bring to bear all the
intellectual resources of the planet; since presumably we have less
to work with, they scaled back. They see the more important aspect
of the simulation as asking what do we do with the CONTENT of the
signals, not, can we decode the content?

(Thanks to John Bray for offering the use of this material.)

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