Optical SETI Survey - General Rationale (Part B)

Radobs 7B

Version 1.0

1.   Life forms are likely to develop eyes whose response peaks up in a
     region of the spectrum to reasonably match the spectral peak of their
     stars.  Do you agree?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


2.   What is more "natural" than to signal in a region of the spectrum where
     the visual response of intelligent life peaks, and in that part of the
     electromagnetic spectrum that tells life forms most about their
     universe.  Do you agree?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


3.   Some have suggested that the reason we have not so far discovered ETI,
     is for the depressingly simple reason that they are not there, in other
     words, we are alone.  However, it may be that we are tuned to the wrong
     frequencies and they are transmitting in the optical spectrum.  Would
     you agree that the latter is a distinct possibility?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


4.   Professor Philip Morrison has suggested to me the following scenario,
     although he doesn't believe in my optical approach.  This scenario,
     which I have called "Signpost SETI", suggests that the acquisition
     signal or beacon that we hope to discover in the 1 GHz to 10 GHz region
     of the microwave spectrum may not be the main signal.  Instead, it may
     just be a very low-bandwidth pointer, signpost or flag, indicating that
     we should tune to another frequency for their main wide-band high-power
     transmission channel.  It is not clear to me why aliens would do this,
     unless a sophisticated encoding system was employed in the main
     channel, or if the main channel was far removed from the signpost,
     i.e., in the infrared or visible spectrum.  Do you think that the
     philosophy of "Signpost SETI" has some merit?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


5.   Beamed or targeted communications are much more efficient, and it is
     unlikely that ATCs would use omnidirectional beams for anything other
     than very low bandwidth signals, because of the wasteful use of power
     and the resulting huge powers involved.
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


6.   It is probably impossible for aliens to dechirp their transmitter in
     all directions for a truly omnidirectional beacon, i.e, they cannot
     remove their local Doppler transmitting frequency shifts and drift due
     to velocities and accelerations along the line-of-sight, simultaneously
     in all directions.  This can only be done efficiently for narrow
     targeted signal beams.  Some theoretical work by Bob Dixon in 1973
     indicates that there are ways to do this at radio frequencies by
     feeding modulated noise into a line array.  Because the technique
     employs a frequency-scanned line source, it is not really compatible
     with anything other than extremely small modulation bandwidths.  It is
     not known how this could be done at optical frequencies.  Do you agree
     that to effectively apply dechirping techniques to wideband systems
     requires narrow beams?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


7.   Free-space optical communications is likely to a very mature technology
     for an advanced technical civilization (ATC).  Do you agree?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


8.   Do you agree with the statement that for an ATC, free-space optical
     communications is "child's play" and is probably easier for them than
     microwave technology is presently to us?  The very high Effective
     Isotropic Radiated Powers (EIRPs) produced by this technology allows
     for very high data-rate communications over vast distances.
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


9.   Of the two principal forms of electromagnetic communication techniques,
     i.e., radio frequency and optical, advanced space-faring civilizations
     are more likely to use optical communications than microwave
     communications for deep-space communication links between their home
     planet, space probes, spaceships or space colonies.  Do you agree?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


10.  It is likely that ATCs will "spin-off" their mature optical
     communications technology for interstellar communication purposes.  Do
     you agree with this statement?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


11.  It could be said that what is alright for NASA should be O.K. for
     aliens, in that JPL is presently conducting advanced research on laser
     communication systems to be used with the next generation of deep-space
     probes.  Do you agree with this general philosophy?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


12.  As mankind moves (emerges) into space, free-space optical
     communications will become our main means of communications with the
     outer reaches of the Solar System.  Do you believe that this will
     happen?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


Score out of 12: YES        =
                 DON'T KNOW =
                 NO         =


December 27, 1990
RADOBS.07B
BBOARD No. 289


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* Dr. Stuart A. Kingsley                       Copyright (c), 1990        *
* AMIEE, SMIEEE                                                           *
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