Project Cyclops, A Design... - Department of Earth and Planetary ...

studies, sowefeelthefollowingstatements canbemade
withgreater conviction thaneverbefore.
CONCLUSIONS
1. It is vastly less expensive to look for and to send
signals than to attempt contact by spaceship or
by probes. This conclusion is based not on the
present state of our technological prowess but on
our present knowledge of physical law,
2. The order-of-magnitude uncertainty in the average
distance between communicative civilizations
in the galaxy strongly argues for an expandable
search system. The search can be begun with the
minimum system that would be effective for
nearby stars. The system is then expanded and
the search carried farther into space until success
is achieved or a new search strategy is initiated.
3. Of all the communication means at our disposal,
microwaves are the best. They are also the best
for other races and for the same reasons. The
energy required at these wavelengths is least and
the necessary stabilities and collecting areas are
fundamentally easier to realize and cheaper than
at shorter
wavelengths.
4. The best part of the microwave region is the low
frequency end of the "microwave window"-
frequencies from about 1 to 2 or 3 GHz. Again,
this is because greater absolute frequency stability
is possible there, the Doppler rates are lower,
beamwidths are broader for a given gain, and
collecting area is cheaper than at the high end of
the window.
5. Nature has provided us with a rather narrow
quiet band in this best part of the spectrum
that seems especially marked for interstellar
contact. It lies between the spectral lines of
hydrogen (1420 MHz) and the hydroxyl radical
(1662 MHz). Standing like the Om and the Um
on either side of a gate, these two emissions of
the disassociation products of water beckon all
water-based life to search for its kind at the
age-old meeting place of all species: the water
hole.
6. It is technologically feasible today to build
phased antenna arrays operable in the 1- to
3-GHz region with total collecting areas of 100
or more square kilometers. The Cyclops system
is not nearly this large, but we see no
technological limits that would prevent its expansion
to such a size.
7. With antenna arrays equivalent to a single antenna
a few kilometers in diameter at both the
transmitting and receiving end, microwave communication
is possible over intergalactic distances,
and high-speed communication is possible
over large interstellar distances. Thus rapid information
transmission can occur once contact has
been confirmed between two civilizations.
8. In the search phase we cannot count on receiving
signals beamed at us by directive antennas.
Neither can we afford to overlook this possibility.
Beamed signals may be radiated at relatively
low powers by communicative races to as
many as a thousand nearby likely stars and for
very long times. Long range beacons, intended to
be detectable at any of the million or so likely
stars within 1000 light-years, will probably be
omnidirectional and very high powered (> 109 W).
9. Beacons will very likely be circularly polarized
and will surely be highly monochromatic. Spectral
widths of 1 Hz or less are probable. They will
convey information at a slow rate and in a
manner that does not seriously degrade their detectability.
How best to respond will be contained
in this information.
10. The efficient detection of beacons involves
searching in the frequency domain with very high
resolution (1 Hz or less). One of the major
contributions of the Cyclops study is a data
processing method that permits a 100 MHz
frequency band to be searched simultaneously
with a resolution of 0.1 Hz. The Cyclops system
provides a receiver with a billion simultaneous
narrow channel outputs. Although the Cyclops
system bandwidth is 100 MHz, no very great
technological barriers prevent widening it to 200
MHz. This would permit searching the entire
"water hole" simultaneously. If our conclusion
as to the appropriateness of this band is correct,
the problem posed by the frequency dimension
of the search can be considered solved.
11. The cost of a system capable of making an
effective search, using the techniques we have
considered, is on the order of 6 to 10 billion
dollars, and this sum would be spent over a
period of 10 to 15 years. If contact were
achieved early in this period, we might either
stop expanding the system or be encouraged to
go on to make further contacts. The principal
cost in the Cyclops design is in the antenna
structures. Adopting an upper frequency limit of
3 GHz rather than 10 GHz could reduce the
antenna cost by a factor of two.
12. The search will almost certainly take years,
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