Optical SETI Survey - Ground-Based and Daylight

Optical SETI (Part F)

Radobs 7F

Version 1.0

1.   Optical SETI is best done in space, and probably has a higher chance of
     success if space-based.  The costs given below are very approximate. 
     Do you think that one or more observatories should be built?  The
     following options are available, depending on mankind's commitment and
     depth of his wallet (tick off the one that you would prefer):

     (a)  A large second-generation Space Telescope at a cost of about
          $10 billion, possibly associated with Space Station Freedom.

     (b)  Two purpose-built ground-based Optical SETI Observatories, one in
          the northern and one in the southern hemisphere, at a total cost
          of about $200 million.

     (c)  The recommissioning of large ground-based telescopes for Optical
          SETI that have been previously decommissioned because of severe
          light pollution effects, at a cost of about $20 million per
          telescope.

     (d)  Adapting existing telescopes and telescopes yet to see first
          light, so that they can be shared with Optical SETI activities,
          with SETI activities being largely relegated to the daytime.  This
          might also be done at a cost of about $20 million per telescope.
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


2.   I have suggested that FIBERDYNE OPTOELECTRONICS & OSU propose to NASA,
     NSF and/or to some private philanthropic organization, to fund a
     project that will develop the receiving and signal processing
     technology for a prototype Optical SETI Observatory.  This might well
     be much smaller than the observatories indicated above.  The optical
     receivers may use heterodyne techniques and PIN photodetector arrays,
     or tunable high-Q Fabry-Perot filters with photon-counting arrays.  Do
     you think that proposing a series of Optical SETI research and
     development programs would be sensible?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO



3.   Do you think a prototype observatory would be useful for perfecting the
     technology?  The prototype Optical SETI Observatory could be built
     around one of the following (tick off the one that you would prefer). 
     Members of RADOBS may have a natural preference for (c), even
     considering the number of overcast days in Columbus.  Remember, night-
     time light pollution should not affect SETI observations, and Perkins,
     outfitted with a new larger telescope, could be made available around
     the clock.  There is plenty of room within the observatory dome to
     house all the needed equipment.  It should be appreciated, that for
     most of the night-time observation periods, it will be possible to
     conduct conventional astronomy and SETI investigations simultaneously
     on the same part of the sky.  The super high resolution light science
     spectral analysis capability of the telescope, will yield valuable new
     data about natural objects in the heavens.

     (a)  The new Columbus Telescope, which is to be constructed on
          Mt. Graham in Arizona.

     (b)  The decommissioned Mt. Wilson Observatory.

     (c)  The Perkins Observatory, adjacent to OSU's "Big Ear" Radio
          Observatory.
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


4.   At the present time, only one of the two 8 meter diameter mirrors for
     the new Columbus Telescope has been paid for.  Do you think it a
     reasonable suggestion that if Optical SETI could make use of this
     telescope, that it might also fund the second mirror?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


5.   In the visible spectrum, dye lasers look very promising for very
     coherent, easily tunable local-oscillator heterodyning sources. 
     Companies like Coherent & Spectra-Physics manufacture these highly
     coherent tunable dye laser systems.  For example, the Coherent Model
     899 Dye Laser can be made to function over the visible and near-
     infrared 380 nm to 1100 nm wavelength band with single-mode linewidths
     as small as 10 kHz, and powers > 200 mW.  The cost of such a system
     with a high-power Ion Laser pump, is likely to be of the order of
     $200,000.  Do you think such a laser has merit for Optical SETI
     receivers?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


6.   Are you an amateur (optical) astronomer?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


7.   If the answer to the above question was YES, it may be possible for you
     to get involved with Optical SETI in the visible spectrum in an amateur
     way.  I would warn, however, that some sophisticated and expensive
     equipment will be required at the receiving end of the telescope.  It
     could be done without (dye) laser local-oscillators and photon-counting
     arrays, though a "poor man's" incoherent approach would require the
     minimum of a high-Q Fabry-Perot interferometer spectrum analyzer and a
     single photon-counting receiver.

     A complete Burleigh CF-500 Confocal Etalon Fabry-Perot system operating
     over the wavelength range 400 - 1400 nm with up to 1.2 MHz resolution,
     costs about $13,000.  Each mirror set, which has a bandwidth of about
     100 nm, costs about $1,300.  Alternatively, the Burleigh HiFASE Etalon
     System can operate over the wavelength region 450 - 1800 nm, with a
     maximum resolution of < 15 MHz, and costs about $ 25,000.  This
     bandwidth is compatible with the maximum bandwidth requirement for
     satisfactory daylight optical SETI.  Each mirror set for this system,
     which covers a bandwidth of about 60 nm, costs about $2,000.

     Initial wavelengths and mirror sets selected would be based on known
     laser or Fraunhofer lines.  Other optical filters or spectrographs
     would be required in order to pre-filter the light and overcome
     problems caused by the Free Spectral Range properties of Fabry-Perot
     interference filters.  Newport Corporation makes a cheaper system
     called the SR Series (465 - 1550 nm), which has a 1.2 MHz passband with
     a 63% throughput, and costs about $7,500.  A single photon-counting
     detector system would cost about $2,000.

     In reality, you would have to be a fairly rich "poor-man", and
     considering the flexibility of the laser heterodyne approach and no
     requirement for a photon-counting array, it could be argued that the
     laser approach is by far the best, albeit somewhat more costly!  The
     cost of the hardware not withstanding, would you be interested in
     amateur Optical SETI?
                                                                            YES
                                                                     DON'T KNOW
                                                                             NO


Score out of 7: YES        =
                DON'T KNOW =
                NO         =


January 1, 1991
RADOBS.07F
BBOARD No. 299


* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* Dr. Stuart A. Kingsley                       Copyright (c), 1991        *
* AMIEE, SMIEEE                                                           *
* Consultant                            "Where No Photon Has Gone Before" *
*                                                   __________            *
* FIBERDYNE OPTOELECTRONICS                        /          \           *
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