Dr.%20H.%20Paul%20Shuch

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The SETI Transmission Debate

• Dr. H. Paul Shuch
• Visiting Professor of Physics
• and Astronomy, Lycoming College
• Executive Director Emeritus,
• The SETI League, Inc.

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Fifty Years of Solitude
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Why not transmit ?
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TV Range Calculations (per Scheffer) Receive
Aperture Ddetect Ddecode (LY) 305 m
(Arecibo) 0.81 0.00081 30 km
(small) 280 0.28 1000 km
(large) 10300 10.3
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Monument to the Martian Invasion of 30 Oct.
1938 Grovers Mill NJ
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transmissions are not all created equal!
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SMI I C
Ordinal Index Parametric Term
Categorical Term
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From SETI 2020

• "Our current electromagnetic leakage within
  narrow portions of the radio bands, outshines the
  Sun by a factor of million.

• "Even an uncorrected omnidirectional radio beacon
  could easiliy outshine the Sun by a factor of
  billion in its band

• "Radio transmissions can routinely outshine the
  Sun with power levels that do not significantly
  add to the Earths energy expenditure.

• "Omnidirectional microwave transmitters can
  continuously outshine the Sun using megawatts of
  power and narrow bandwidths of approximately 1
  Hz."

• "In the microwave, a beacon must emit about 1
  kW/Hz to outshine the Sun."

• most SETI radio signals are likely to be much
  brighter than the adjacent star."

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I intensity of the transmission
Average solar flux density in the frequency band of the transmission (Io) 0
10 Io 1
100 Io 2
1000 Io 3
10 000 Io 4
?100 000 Io 5
I is the Common Logarithm of the Intensity
Ratio (think Bels over Background)
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http//iaaseti.org/SMI_I.xls
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C character of the transmission
A beacon without any message, e.g. planetary radar 1
Message with the intention to reach ETI at arbitrary directions for minutes or hours, 2
Special signal in a preselected direction at a preselected time in order to draw the attention of ET astronomers 3
Continuous, broadband transmission of a message to ETI 4
Reply to an extraterrestrial signal or message (if they are not aware of us yet!) 5
C is a numerical value assigned to a Categorical
Designator
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• Integer
• Ordinal
• Categorical

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SMI as a Policy Tool

• Rather than forcing blanket policy decisions
  about whether or not to allow transmissions, each
  potential signal must be quantitatively analyzed,
  and judged on its own merit and risk.

• At about SMI3 and below, a transmission is of
  negligible impact (no regulation required).

• At about SMI8 and above, impact is significant
  (perhaps prohibitions are in order).

• In between, evaluate on a case-by-case basis.

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• http//iaaseti.org Click on Protocols
  Follow the link to the San Marino Scale

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Emily Dickinson, circa 1884
We send the Wave to find the Wave An Errand so
divine,
The Messenger enamored too, Forgetting to
return, We make the wise distinction
still, Soever made in vain,
The sagest time to dam the sea Is when the sea
is gone.
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• CONTACT

Dr. H. Paul Shuch Executive Director Emeritus The
SETI League, Inc. www.setileague.org paul_at_setileag
ue.org