slide description containing various interstellar communication techniques,its scope,viability and also about recent developments

1. PRESENTED BY:
AKHIL SOHAN
S7 ECE B
ROLL NO:2
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2. • Transmission and reception of signals between
planetary systems
• Planetary systems can be located in two different
galaxies
• Low energy radio waves are used
• Low frequency radio waves penetrate earth’s
atmosphere and pass through interstellar space
• Mainly used for finding ET’s(extraterrestrial
intelligence) and also used in pulsar astronomy
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3. STARSHIPS
• Two way communication
• Should travel at speed of light
• High downlink rate
• Relativistic effect can hamper wave propagation
CIVILIZATIONS
• Establishment of two way communication difficult
• Composition of message prior to our/their
knowledge
• Chance of impairments at thousands of light years
due to scattering effects
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4. ENERGY
• Energy factor critical in information
transmission
• Propagation loss compensated by larger
antennas or increasing transmit power
• Omnidirectional transmit antenna used
• Reducing transmission energy can be
beneficial
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5. • Equation to estimate the number of civilizations currently
communicating in our Galaxy
Ncivil = N*  fp  np  fl  fi  fc  fL
Where,
N* = the number of stars in the Milky Way
fp = the fraction of stars that have “habitable planets”
np = the number of habitable planets per system
fl = the fraction of habitable planets where life evolves
fi = the fraction of life-planets that evolve intelligence
fc = the fraction of civilizations that communicate
fL = the fraction of the star’s life that the civilization exists
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7. • Range of frequencies with minimum
background radio noise
• Frequency range from
1.42Ghz(emission of H atom) to
1.721Ghz(emission of OH molecule)
• Messages from civilizations may be
gathered from this frequency range
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• It is a directional radio antenna
• Differs from optical telescope as it uses
radio frequency in electromagnetic
spectrum
• Large parabolic dish antenna,used singly
or in an array
• Isolated from populated areas
• Radio telescopes in array uses radio
interferometry

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ARECIBO RADIO TELESCOPE

11. DELIBERATE SIGNALS
• Sent in hopes that another civilization will receive them
• Radio waves are used
• Frequencies between a few hundred Mhz and a few
thousand Mhz are best
• ‘’Spin flip’’ transition frequency in H atom=1420 Mhz
in OH atom=1721 Mhz
• H and OH atoms radiate itself at this frequencies
causing background noise
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12. ACCIDENTAL SIGNALS
• Used by civilizations for other purposes, but
escapes into space inadvertandly
• TV and FM radio transmissions have been
leaving earth since about 1940.
• They have made it a little over 60 ly in that
time (reached 2500 stars)
• Effect of doppler shift due to earth’s rotation
about sun
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13. • It may contain pictures or simple coded
language
• Math can be used to transmit a picture(binary
coding)
• Mathematics provide a universal language
that any technological civilization would
understand
• Pictures may depict the image of human
race,DNA,radio telescope,location of earth in
solar system,location of solar system in milky
way galaxy,as per the ideas known to us
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15. • Usage of multiple images to indicate
motion
• Increasing the resolution of the image
• Using better coding techniques after
successfully exchanging the information
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16. LASER COMMUNICATION
• Signal tightly collimated –energy
concentration single direction
• Visible light(LASER) easier to use than radio
wave or microwave(MASER)
• Good for interstellar communication if
location is accurately known
• Possibility of getting accidental signals are
very low
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17. NEUTRINO
• Neutrino is a subatomic particle produced by
cosmic rays in earth’s atmosphere
• Neutrino communication is advantageous as it has
low probability of interacting with any other
matter
• Apparatus sensitive to wide-range
• Superkamiokande detector is used for neutrino
detection
• Means of detecting neutrinos are relatively
insensitive with current technology
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18.  SETI(Search for extraterrestrial intelligence)
• Started in the early 1970’s by NASA
• With main aim as to identify intelligence from another
communicating civilization
• Established SETI programs as NASA’s AMES and JPL
• AMES-can do target searches
• JPL-can do sky surveys
• NASA funding from 1988-1993
• Since then scaled down versions have been privately
funded
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19.  PROJECT OZMA
• Frank Drake in 1960 independently came up with the same
conclusion.
• Used a 26m radio telescope at Green Bank, West Virginia
• Searched for ETI for 2 weeks.
• Called it Project Ozma (L. Frank Baum’s Land of Oz - “very far
away,difficult to reach, and populated by strange and exotic beings”)
• Looked at Tau Ceti and Epsilon Eridani (stars about same age
as the sun)
• Looked for repeated series of patterned pulses or a series of
prime numbers.
• Showed systematic searches are feasible and eventually led to
a small SETI program at NASA in the 1970’s
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20.  PROJECT PHOENIX
• Started in 1995
• Targeted search of local objects in the sky within 200
light years
• Examining 1,000 nearby stars using the world’s largest
antennas
• Monitors millions of radio channels simultaneously
between 1,000-3,000 MHz.
• Looking for narrow band signals.
• By mid-1999 had examined 50% of stars on its “hit list”
• Listening done automatically
• Two billion channels examined for each target star
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21.  OPTICAL SETI at licks observatory
• Communicating by visual signals (e.g., lasers).
• Requires more energy to send signal (than radio).
• Tends to absorbed by dust grains in interstellar space.
• Could use short bursts of laser light, into a Morse
code.
• Should be immune to “false positives” from Radio SETI.
• looking for laser pulses (billionth of a second long).
• new technology makes this search possible.
• uses a telescope and three photomultipliers, built by
UC Santa Cruz undergrad physics major.
• examined 300 stars and a few star clusters.
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22. Allen Telescope Array
• Funding from Paul Allen and Nathan Myhrvold
• Being constructed for SETI use and radio
astronomy.
• Joint effort by SETI and UC Berkeley.
• Built at Hat Creek Observatory north of Lassen
Peak.
• Will expand Project Phoenix to 100,000-1,000,000
stars
• Will cover 1,000-10,000 MHz
• Will be 350 - 6.1m antennas, randomly placed in 1
km diameter area.
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23. • The distances involved imply large
transmitted power and/or large antennas
• The costs can be mitigated by reducing
the energy delivered to the receiver
• Requires an end-to-end communication
system
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24. • en.wikipedia.org
• D.G. Messerschmitt, ”Design for minimum
energy in starshipand interstellar
communication”submitted to the Journal of
the British Interplanetary Society (available at
arxiv.org/abs/1402.1215).
• seti.org
• astronomytoday.com
• Rohlfs, K., & Wilson, T. L. (2004). Tools of
radio astronomy. Astronomy and astrophysics
library. Berlin: Springer.
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