LISTENING FOR SIGNALS
Anant Konanahalli
Kristine Werling
John Toman
Ellie Bensinger
Mission Def-D-6
“Define Drake’s 6th Variable”
Fc = fraction of civilizations that develop a technology
that releases detectable signs of their existence into
space.
Why listen for signals?
• The ability of an extraterrestrial civilization to send a
signal would indicate their presence and intelligence.
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What are we looking for?
 “Radio signals coming from outer space that
have no causal factors” –SETI
 “Narrow-bandwidth radio signals: --SETI
 Not known to occur naturally
 Indicate artificial source = Extraterrestrial Life
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Def-D-6 Plan Proposal
Focus Projects
1) Allen Array Telescope
2) Big Ear
3) SETI@home
Projects to Cut
1) CETI
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Allen Telescope Array: What is it?
 ‘One Hectare Telescope’
 2007 at Hat Creek Observatory, Cascade Mountains
 SETI Institute + Radio Astronomy Laboratory
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Allen Telescope Array: What does it do?
 Purpose Two-Fold
 Conventional radio astronomy projects
 SETI
 SETI Focus
 1) Sky sweep survey
 2) Targeted Searches
 Data collected
 4.5 octaves of frequency
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Allen Telescope Array: How does it do it?
 LNSD array = Large Number of Small Dishes
 42 dishes
 Pseudo-random arrangement
 1 km circle
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Allen Telescope Array: How does it do it?
• Basic Signal Collection
Radio
waves
collected at
antenna
Radio
waves
focused
Converted
to electrical
signals
Amplified
Processed
Beam Width
Limitation:
Sinθ= 1.22λ/D
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Allen Telescope Array: How does it do it?
• Array Advantage
 Combined to form equivalent of single large dish
Beam Width
Limitation:
D
Sinθ= 1.22λ/
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Allen Telescope Array: How does it do it?
 Adjustments to ‘listen’ in different directions
 Alter cable lengths and electronic delays
 Bring waves from different direction in-phase
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Allen Telescope Array: How does it do it?
 Offset Optic or Gregarian Antenna System
“Because sometimes, as in football, going to the side can reduce
interference”
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Allen Telescope Array: Why Invest?
 Array vs Single Large Disk
 Lower cost
 Easier adjustments/repairs
 Easy to add on/improve
 Multipurposed
 Radio astronomy
 SETI
 Speed up SETI searches
 24hr data collection
 Simultaneity
 Larger sky area
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Allen Telescope Array: Modifications
 Expand to the “Square
Kilometer Array”
 Expand to 350 dishes
 Angular resolution of 700
meter diameter dish
 Comparable to Robert C.
Byrd Telescope and Very
Large Array
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Ohio State University Radio
Observatory (Big Ear)
 John D. Kraus, built/design
 Small Ear Prototype
 NSF grant to start Big Ear
 Considerably less than req’d
 Had to scale down
 2000 ft.360 ft. in length
 Main Components
1.
2.
3.
Flat Reflector
Paraboloidal Reflector
Feed Horns
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Big Ear: Flat Reflector
 340 ft. x 100 ft.
 Wire Mesh
 Ability to tilt
 Unfocused
waves
 Ground Plane
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Big Ear: Paraboloidal Reflector
 360 ft. x 170 ft.
 Focused the sent waves
 Wavelengths
 ~21.1 cm (8.3 inches)
 1411-1420 MHz
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Big Ear: Feed Horns
 Two Horns
 Funneled waves
 Signal Switch
(79x)
 Why Switch?
See the same area twice in 2.5-5 minutes
2. Removed variation due to drift and sky variation
1.
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Big Ear: Recap
Big Ear: WOW! Signal
 Jerry R. Ehman 1977
 Coded Intensity
 Found at 1420 MHz
 Sagittarius
 Lasted 72 seconds, not replicated
 Even Very Large Array could not detect
Earth-borne signal reflected off space debris
2. One-time burst
1.
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Big Ear: Justifications for Use
 Started from NSF grant of $48,000

$450,000 today with inflation
 Need to resolve this signal via further
investigation

Physically impossible for WOW! to bounce off of
debris, 1420 MHz is restricted, something is up.
 Very Large Array ($78.5M) is very similar and
has made key observations of black holes
and protoplanetary disks.
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SETI@home: Overview
• Released to the public in May of 1999
• Over 5 million users worldwide
• Has completed 2 million hours of computing time
Primary Goals
1) to do useful scientific work by supporting an observational
analysis to detect intelligent life outside Earth
2) to prove the viability and practicality of the 'volunteer
computing' concept.
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SETI@home: How it Works
 Searches for possible
radio transmissions
from ETs
 Uses observational
data from Arecibo
 Data digitized and sent
to SETI@home
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SETI@home: How it Works
 Parses data into millions of very
small chunks
 Anyone can download software
onto their computer
 Personal computers use
processing power to analyze
these chunks (variations)
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SETI@home: Justifications
 SETI@home doesn’t use government
funding
 Berkeley has found ways to work with small
budgets and donations
 Increasing power of home computers/laptops
 Other applications of interest
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SETI@home: Possible Modifications
 Alternative to Arecibo telescope
 Better hardware quality
 Increased marketing efforts
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CETI
 Communication with
Extraterrestrial Intelligence
 Subset of SETI
 Researching effective means
of communication
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Previous CETI projects
 Arecibo Message (1974):
 Radio message to starcluster M13
 Binary- DNA, Map of Solar System
 Cosmic Calls 1 and 2 (1999)
 Sent to several stars
 Contained text, audio, video, “Rosetta Stone”
version of Arecibo
 Doritos Commercial
(2008)
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CETI entails…





Hiring social scientists: Douglas Vachok
Creating mathematical and scientific languages
Creating pictorial languages
Lincos: Lingua cosmica
Figuring out best representation
 Binary, Radio, Pulse
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Noble but not necessary yet…
 Already so much data to decode
 “Linear A” problem
 Un-decoded early human language
 SETI- Interstellar Message Composition
 Closest Earth like planet: Gliese 581 system
 20 light years away
 40 year exchange
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First Things First
 Fund programs that are looking for incoming
data
 Most likely way of detecting life
 Once we find something, then maybe CETI
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References

Douglas A. Vakoch. "To the Stars, Silently." Leonardo 37.4 (2004): 265-265. Project MUSE. Web. 7 May. 2013.
<http://muse.jhu.edu/>.

Douglas A. Vakoch. "The Art and Science of Interstellar Message Composition." Leonardo 37.1 (2004): 32-34.
Project MUSE. Web. 7 May. 2013. <http://muse.jhu.edu/>.

Freudenthal, Hans. Lincos; Design of a Language for Cosmic Intercourse. Amsterdam: North-Holland Pub., 1960.

"SETI Institute." SETI Institute. N.p., n.d. Web. 07 May 2013.
http://www.redorbit.com/media/uploads/2004/10/6_3e3fcbe6f4bfa435cdb6eeb6ff721f3c2.jpg
http://www.setileague.org/photos/miscpix/drakeqn.jpg
http://www.scienceprog.com/wp-content/uploads/2008i/DSP1/Radar_location_and_DSP.gif
http://voices.yahoo.com/seti-detects-alien-signal-outer-space-we-are-2745373.html
http://setiathome.berkeley.edu/sah_about.php
http://openseti.org/OSSearch.html
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