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EJASA - Part 8


                                                                     Page 50

        Even as this is being written, substantial developments are being
    made in terrestrial video compression techniques for High Definition
    TeleVision (HDTV).  Compression ratios as high as 100:1 have been
    achieved with only a small reported impairment in perceived video
    quality. [87]  A 100:1 compression ratio would reduced bandwidth
    required by the digitized video signal by a factor of 100.  If it was
    applied to an ETI interstellar communication system, the effective CNR
    could be increased by 20 dB.  Of course, we cannot yet comment on
    whether ETIs would use such techniques, or what their level of
    sophistication is.  What we can say, however, is that optical communi-
    cations technology, along with video compression techniques, would make
    it much easier to transmit high-quality "real-time" video signals over
    thousands of light years.  What was previously thought possible with
    old-fashioned analog TV signals and a 1 GW transmitter over ten light
    years now becomes possible over one hundred light years.

        ETI signals may be linearly or circularly polarization-modulated,
    so that as previously mentioned, some means of analyzing the light would
    be required to detect the modulation.  This polarization analyzing
    system could include a polarizer and a Soleil-Babinet compensator or
    quarter/half-wave retardation plates.  The latter might be spun to
    cause sampling of all polarization states.  If the signals are
    frequency (or phase) modulated with relatively small deviations, then
    only the professional heterodyne receiver will be able to recover the
    modulation envelop, whatever the signal strength.


        Shopping List -

     1.  8"-14" (20-36 cm) or larger Schmidt-Cassegrain with periodic error
         correction drive and RS-232 or IEEE-488 interface.

                 Low $2,000                          High $12,000

     2.  CCD imaging and tracking system with RS-232 or IEEE-488 interface.

                 Low $1,100                          High $3,200

     3.  Polarizaton analyzer.

                 Low $100                            High $2,000

     4.  Fiber-optic umbilical and connectors (ten meters).

                 Low $150                            High $150

     5.  Triple grating monochromator (resolution 0.1 to 0.01 nm) with
         RS-232 or IEEE-488 interface.

                 Low $1,000                          High $6,500

     6.  APD photon-counter or photomultiplier front-end.

                 Low $200                            High $3,000

    EJASA, Vol. 3, No. 6, January 1992
                                                                     Page 51

     7.  Front-end cooling system.

                 Low $200                            High $1,000

     8.  PC with fixed (hard) disk and RS-232/IEEE-488 interfaces.

                 Low $1,000                          High $3,000

     9.  Spectrum analyzer PC card or stand-alone 0-10 MHz spectrum
         analyzer.

                 Low $1,000                          High $4,400

    10.  Video and audio monitors (PC may double-up for this purpose).

                 Low $200                            High $200

    11.  Miscellaneous

                 Low $1,000                          High $2,000

    12.  Labor - Free

           Total cost: Low $8,000; High $38,000

 
        Thus, the low-end cost is approximately $8,000; less if telescope
    and computer system are already available.  This is an affordable
    activity for many clubs and societies.  Some of the equipment above is
    optional and may be replaced by less sophisticated devices, e.g., the
    automatic scanning monochromator could be replaced by a manual
    monochromator or a series of discrete high-Q bandpass filters, such as
    a 656 nm H_alpha filter.  By omitting the electrical spectrum analyzer
    and using a fixed optical bandpass filter, instead of a scanning
    monochromator, the cost of a rudimentary system adaptation to an
    existing telescope would fall to about $3,000.  This figure will be
    affordable for some individual enthusiasts.

        Instead of a scanning grating monochromator, a scanning grating
    spectrometer might be used, where a linear CCD array is employed to
    produce an essentially instantaneous display of optical spectra (over a
    limited band) on a video display terminal (VDT).  However, this does
    not allow for the flexibility of employing a single photodetector
    optimized for bandwidth and photon-counting sensitivity, and thus this
    approach will be more expensive and/or less sensitive.  Often, mono-
    chromators use triple gratings in order to obtain spectral resolutions
    of 0.01 nm or better.  As previously mentioned, a set of four optical
    fibers surrounding the signal fiber and corresponding low-bandwidth
    photodetectors might be used in the system for fine guidance purposes.

        Within this account of Amateur Optical SETI is the ambitious
    desire to detect the modulation envelop.  Hopefully, the ETI signals
    will be intensity or polarization-modulated so that the modulation can
    be detected by an incoherent receiver.  For weak signals, we may only


                                                                     Page 52

    be able to detect the presence of an optical carrier or beacon (perhaps
    Signpost SETI) and then only after some signal integration.  However,
    this would be a significant achievement by itself, allowing for more
    powerful professional receivers to be built later for detecting the
    modulation envelope.

        As a spin-off from the MOP, electronic Multi-Channel Spectrum
    Analyzers (MCSAs) could be developed for the Amateur Optical SETI
    market, eventually making Amateur Optical SETI an even more affordable
    activity for optical astronomy clubs and societies.  Perhaps ETIs do
    not expect their signals to be detected until the targeted civili-
    zations make a collective, cooperative, and systematic search of their
    home skies!


              THE MICROWAVE AND OPTICAL OBSERVING PROJECT (MOOP)

        The following is the author's tentative list of objectives for the
    optical extension to MOP.  It is called the Microwave and Optical
    Observing Project, otherwise known by the acronym MOOP.

        Project Goal:  To continue the search for microwave (and millimeter
                       wave) signals of extraterrestrial intelligent origin
                       and to extend the search into the infrared and
                       visible spectrums.

        Project Objectives:

        1.  To use existing large ground-based optical telescopes to carry
            out a Targeted Search of about 800 nearby solar-type stars with
            spectral resolution of 1 kHz and sensitivity 10^-16 W/m^2.
            For selected laser wavelength bands corresponding to
            atmospheric windows in the visible and infrared wavelength
            range (350 nm to 12,000 nm).

        2.  To use existing large ground-based optical telescopes to carry
            out a Targeted Search of about 1 million nearby solar-type
            stars with spectral resolution of 100 kHz and sensitivity
            10^-10 W/m^2.  For selected laser wavelength bands corres-
            ponding to atmospheric windows in the visible and infrared
            wavelength range (350 nm to 12,000 nm).

        3.  To use dedicated groups of amateur astronomers and coordinate
            their activities to conduct with their ground-based optical
            telescopes a low-sensitivity Targeted Search of about 800
            nearby solar-type stars with spectral resolution < 1 nm, and
            sensitivity 10^-16 W/m^2.  For selected wavelength bands in the
            visible and near-infrared wavelength range (350 nm to 1,200 nm).

        Duration:  2001 - 2010

        Cost:  $20M for starters.  Assumes use of existing large ground-
               based professional telescopes and the cost of modifying the
               telescopes for adaptive reception and Optical SETI.

  
                                                                     Page 53

 ==========================================================================
     Table 5  Nearest stars favored for MOP's 800 star Targeted Search

 ==========================================================================
  RGO        RH         DEC    Relative  Distance  Apparent   Spectral
 Number    H  M  S     D  M    Vel. km/s   L.Y.    Magnitude    Type
 --------------------------------------------------------------------------
 559A     14 36 11   -60 37.8    -22.2     4.39    -0.01     G2  eye, SB
 559B     14 36 11   -60 37.8     -0.0     4.39     1.33     K0  eye
 144       3 30 34    -9 37.6    +15.4    10.79     3.73     K2  eye
 820A     21  4 40    38 30.0    -64.3    11.01     5.22     K5  eye, AB
 820B     21  4 40    38 30.0    -63.5    11.01     6.03     K7  eye
 845      21 59 33   -56 59.6    -40.4    11.20     4.69     K4  eye
  71       1 41 45   -16 12.0    -16.2    11.77     3.50     G8  eye
 380      10  8 19    49 42.5    -26.0    14.68     6.59     K7
 166A      4 12 58    -7 43.8    -42.4    15.90     4.43     K1  eye
 702A     18  2 56     2 30.6     -7.2    16.72     4.03     K0  eye, UD
 702B     18  2 56     2 30.6    -10.0    16.72     6.00     K5  eye, SB
 663A     17 12 16   -26 31.8     -0.7    17.25     4.32     K0  eye
 663B     17 12 16   -26 31.9     -0.2    17.25     5.10     K1  eye
 570A     14 54 32   -21 11.5    +19.5    18.11     5.78     K5  eye
 664      17 13  9   -26 28.6     -1.3    18.31     6.34     K5
 783A     20  7 55   -36 13.7   -130.3    18.42     5.31     K3  eye
 764      19 32 28    69 34.6    +26.7    18.52     4.69     K0  eye
  34A      0 46  3    57 33.1     +9.4    18.94     3.44     G0  eye
 139       3 17 56   -43 15.6    +86.8    20.25     4.26     G5  eye
  66A      1 37 54   -56 26.9    +22.5    21.32     5.07     K0  eye
  66B      1 37 54   -56 26.9    +19.4    21.32     5.90     K0  eye
 566A     14 49  5    19 18.4     +3.9    22.03     4.54     G8  eye
 566B     14 49  5    19 18.4     +5.4    22.03     6.91     K5
 892      23 10 52    56 53.5    -17.8    22.18     5.57     K3  eye
  33       0 45 45     5  1.4    -12.6    22.62     5.75     K2  eye
 105A      2 33 20     6 39.0    +23.4    22.64     5.82     K3  eye, UD
 667A     17 15 33   -34 56.2     +1.2    23.29     5.91     K3  eye
 667B     17 15 33   -34 56.2     -0.0    23.29     7.20     K5
  17       0 17 29   -65 10.1     +8.8    23.44     4.23     G0  eye
  68       1 39 47    20  1.6    -33.7    24.32     5.24     K1  eye
 178       4 47  7     6 52.5    +24.3    24.70     3.19     F6  eye
 673      17 23 16     2 10.2    -28.3    24.70     7.53     K7
 666A     17 15 15   -46 35.1    +23.6    24.89     5.48     G8  eye
 713      18 21 58    72 42.7    +32.5    25.27     3.58     F7  eye, SB AB
 879      22 53 37   -31 49.8     +9.0    25.47     6.49     K5
 117       2 50  7   -12 58.3    +18.8    25.67     6.05     K0
  23A     11 15 31    31 48.6    -15.5    25.67     3.79     G0  eye, SB AB
 423B     11 15 31    31 48.6    -15.9    25.67     4.80     G0  eye, SB
 216B      5 42 21   -22 26.2    -10.1    26.50     6.15     K2
 216A      5 42 23   -22 27.8     -9.7    26.50     3.60     F6  eye
 502      13  9 32    28  7.9     +6.1    27.17     4.26     G0  eye
 785      20 12 10   -27 11.0    -54.2    27.17     5.73     K0  eye, SB
 506      13 15 47   -18  2.0     -8.5    27.39     4.74     G6  eye
 827      21 22 20   -65 35.6    -29.5    28.10     4.22     F6  eye
 231       6 11 44   -74 44.2    +34.9    28.35     5.08     G5  eye
  75       1 44  6    63 36.4     +1.8    28.59     5.63     K0  eye
 ==========================================================================


                                                                     Page 54

        Table 5 is an extract from the list (provided by the SETI
    Institute) of the closest stars that form the group of 800 stars which
    are subject to MOP's "Targeted Search". [40-45]  Presently, the list
    covers stars in the range of 4.39 to 81.5 light years from Earth, but
    is subject to review.

        UD  = White Dwarf                     559A = Alpha Centauri A
        EB  = Eclipsing Binary                144  = Epsilon Eridani
        AB  = Astrometric Binary               71  = Tau Ceti
        SB  = Spectral Binary
        eye = Visible to the unaided eye under good conditions (apparent
              visual magnitude less than 6.0 - about 224 stars).


        The Amateur Optical SETI system just described is quite capable of
    being upgraded in sensitivity by slaving "n" similar telescopes
    together, and combining the photons from the "n" optical fibers through
    a single monochromator and photon-counter.  In this way, ten telescopes
    of 25-cm (10") aperture would have approximately the same sensitivity
    as a single 81-cm (32") telescope, but in a more cost-effective manner.
    Of course, ten small telescopes would not have the same ability as a
    32" (81 cm) telescope to reject the effects of daylight, should
    daylight Optical SETI be desired.  The approach could be adopted, as
    with the original Cyclops Study, to gradually increase the number of
    telescopes as the need arises and availability of funding, assuming
    that ETI signals are not detected soon after system activation.

        A large, single barrel, telescope could be constructed using
    several smaller mirrors, each with its own focus and optical fiber.  In
    this way, only one drive system would be required.  A much simpler
    construction is possible because we do not need to image a star field,
    just collect as many photons as possible from the region around a
    single star (light-bucket mode of operation).  This could be somewhat
    like the Multi-Telescope Telescope (MTT) that has been designed by
    Georgia State University's (GSU) Center for High Angular Resolution
    Astronomy (CHARA). [92]


              LIST OF PREVIOUS AND PRESENT OPTICAL SETI ACTIVITIES

        The following material has been extracted from a comprehensive list
    on all modern-day SETI activities so far, and was prepared in October
    of 1991 by Dr. Jill Tarter of the SETI Institute.

        Dr. Tarter lists sixty three different SETI observing programs,
    starting with Project Ozma in 1960 at the Green Bank National Radio
    Observatory in West Virginia, to Harvard University's microwave search
    of Messier M31 and M33 from the Oak Ridge Observatory.  This list also
    includes the 1983-1984 Amateur Microwave SETI program organized by
    Dr. Kent Cullers, which used Silicon Valley Hams with their satellite
    TV dishes (TVROs).

        Of this list of sixty three observing programs, only three were or
    are concerned with Optical SETI, and these optical programs are listed


                                                                     Page 55

    below.  Optical SETI observing programs currently amount to less than
    5 percent of all SETI programs to date.  In actuality, the ratio is
    nearer 3 percent because Shvartsman's two programs can be considered as
    one.  This supports the author's contention that Optical SETI has
    suffered benign neglect.


    Date:                         1973 - 1974
    Observer(s):                  Shvartsman et al. "MANIA"
    Site:                         Special Astrophysical Observatory
                                  (former Soviet Union)
    Instrument Size (m):          0.6
    Search Wavelength (nm):       550
    Frequency Resolution (Hz):    df = 100 kHz (dWl = 10^-7 nm)
    Objects:                      21 Peculiar Objects
    Reference:                    48
    Comments:                     Optical search for short pulses of length
                                  3 X 10^-7 to 300 seconds, and narrow
                                  laser lines.  Prototype for later system
                                  on 6 m telescope.

    Date:                         1978 to Present
    Observer(s):                  Shvartsman et al. "MANIA"
    Site:                         Special Astrophysical Observatory
                                  (former Soviet Union)
    Instrument Size (m):          6
    Search Wavelength (nm):       550
    Frequency Resolution (Hz):    df = 100 kHz (dWl = 10^-7 nm)
    Objects:                      93 Objects
    Flux Limits:                  < 3 X 10^-4 of the optical flux is
                                  variable in any object observed.
    Total Hours:                  250
    Reference:                    54 and 58
    Comments:                     Have searched 30 Radio Objects with
                                  Continuous Optical Spectra to date,
                                  looking for optical pulses from
                                  potential Kardashev type II or III
                                  civilizations.

    Date:                         1990 to Present
    Observer(s):                  Betz
    Site:                         Mt. Wilson
    Instrument Size (m):          1.65 m element of Townes IR
                                  Interferometer
    Search Wavelength (um):       10.6
    Frequency Resolution (Hz):    3.5 MHz (35 m/s)
    Objects:                      100 nearby solar-type stars
    Flux Limits:                  1 MW transmitter out to 20 psc
    Total Hours:                  Continuing
    Reference:                    57
    Comments:                     Search for IR beacons at CO2 laser
                                  frequency using narrowband acousto-
                                  optical spectrometer.



Continued

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