SPIE's OSETI III Conference (No. 4273)
The Search for Extraterrestrial Intelligence (SETI)
in the Optical
1993, the first SPIE conference on the Search for Extraterrestrial Intelligence
in the Optical Spectrum (Optical SETI) was held in Los Angeles with the keynote
address given by Sir Arthur C. Clarke.
This was followed by a second conference in 1996, which was held in San
Jose. The keynoter then was
Professor Ron Bracewell.
The third conference this year was again held in San Jose with the
keynote address being given by Professor Chandra Wickramasinghe. SPIE’s
OSETI III conference celebrated the 40th Anniversary of Optical SETI.
A surprise award was made to Professor Charles Townes on the first day of
the meeting to mark the occasion. He
was honored for his major contributions to Optical SETI, from both the laser and
optical search perspectives. Pictures
from this award presentation are included at the end of Professor Townes’
paper. The first day of the
conference was also the occasion for a lunchtime press conference by the
Planetary Society to launch the new Harvard dedicated OSETI observatory.
3rd SPIE international OSETI conference was a significant conference
because it comes at a time when the optical approach to SETI is receiving
greater acceptance from the SETI community at large. It has taken forty years for this to come about.
Robert Schwartz and Charles Townes published the first seminal paper on
Optical SETI in 1961 in the British journal Nature.
They suggested that continuous wave lasers could be used for interstellar
communication. Since the laser had
recently been invented, their power output was miniscule.
The scientific SETI community did not consider an optical search for
laser beacons to be a serious alternative to the microwave search advocated by
Cocconi and Morrison in the earlier 1959 paper, which was published in the same
the next few decades, discussions continued to be held as to the merits and
demerits of the use of lasers for interstellar communications.
Notably Shvartsman and Beskin in the former Soviet Union conducted a few
sporadic searches in the optical regime. But
by and large no serious dedicated attempt was made to embark on a large scale
Optical SETI search until 1998. In
the intervening years, the technology of optoelectronics or photonics had
reached a level of maturity such that lasers, rather than radio waves, now
conveyed most of the data produced on this planet.
It is for this reason that the modern definition of the terms ‘Optical
SETI’ or ‘OSETI’ now covers that part of the electromagnetic spectrum
stretching from the far infrared to the ultraviolet.
years after Schwartz and Townes’ paper, Monte Ross proposed that substantial
benefits could be gained by using nanosecond laser pulses for interstellar
communications. This new direction
in interstellar communication coupled with the exponential growth of laser power
over the past several decades, lent credence to the Optical SETI search.
In his retrospective address to the conference, Townes said, “Just what
technology an advanced civilisation would have is still debatable, but on earth
communication with lasers is growing rapidly and now 'Optical SETI' seems to
many a likely prospect. In addition
to increased power and variety of lasers, with expectation of further growth,
the easy use of short pulses alleviates the need for high spectral resolution by
CW laser communication, and gives high signal to noise ratios.
Such changes in our technology over only a few decades obviously
stimulate open-mindedness about the state of technical development and
communication in any external civilisation.”
Already on present day Earth there is a tremendous drive to develop
optical communications rapidly. According
to Hamid Hemmati, “Future NASA and commercial space missions will require
communications terminals to provide higher data rate with lower mass and
power”. All this looks very
promising for a search to be made for optical interstellar communications by ETI
searches by Viktor Shvartsman, Albert Betz and Stuart Kingsley led in the 1990s
to the mounting of a series of new dedicated searches by a number of groups in
the USA and Australia, viz: Paul Horowitz and his group at Harvard and Princeton
Universities, Dan Werthimer at the University of California Berkeley, Remington
Stone at Lick Observatory and Ragbir Bhathal at the University of Western
were 31 papers on various aspects of Optical SETI and SETI presented at the
conference. They ranged from the
theory of panspermia to spaced based Optical SETI.
The papers were both imaginative and thought provoking with many new
ideas for comment and critical discussion.
conference began with a keynote paper by Chandra Wickramasinghe and Sir Fred
Hoyle on the controversial theory of panspermia and its implications for SETI.
According to Wickramasinghe, “there is clearly no logic whatsoever that
constrains the origin of life to a warm little pond on Earth.
Panspermia offers a totally different landscape on which the logic of
SETI can be restored”. He
supported his thesis with a number of examples, which seemed to indicate that
bacteria could survive under extreme conditions and hence may have been
responsible for seeding Earth with life. In
supporting the panspermia theory, Brigham Klyce noted that the “mere
possibility of panspermia unhinges the Darwinian account of evolutionary
progress”. This year’s SPIE
President, Richard Hoover, brought to the attention of delegates that the
detection of chemical biomarkers and possible microfossils in the ancient Mars
meteorite (ALH84001) by McKay has triggered the development of the rapidly
emerging field of astrobiology. New
research is being carried out to recognise biomarkers as well as trying to gain
an understanding of the environmental conditions under which microbial
Boden extended Hoover’s paper by speaking about NASA's Origins Program.
The program seeks to answer two of humanity's most persistent questions:
Where do we come from? Are we alone? According
to Boden, “While the questions are challenging, our generation is privileged
to have the technological ability to reveal the possibilities for the first
time. Just as the Greeks were known
for democracy, the Egyptians for pyramids, and the Romans for roads, our
civilization may well be remembered for discovering life beyond our own planet,
forever changing our perception of the Universe and our place in it.”
Barrie Jones examined the question of whether terrestrial planets could
exist in the habitable zones of known exoplanetary systems.
To answer this question, he employed numerical integration to the Rho
Coronae Borealis and 47 Ursae Majoris systems.
He said he found that “over much of the parameter space defining the
launch orbit of a terrestrial planet, the terrestrial planet remains in the
habitable zone for billions of years”. This
implies that the occurrence of intelligent species on terrestrial planets in
these systems cannot be ruled out. On
another note, Robert Bradbury examined the question of life at the limits of
physical laws. He proposed a number
of characteristics which intelligent technological life should possess at the
limits of physical laws. Some of
these characteristics include thought capacities in excess of a trillion
trillion times that of an individual human, survival times of trillions of years
and astronomical observational capacities trillions of times greater than our
discussion about the origin of life and microbial forms of life brought up the
vexed question of the “L” factor in the Drake equation.
Mark Ciotola began his analysis by examining the potential components of
L, viz: quantity of fossil fuel reserves, solar energy potential, quantity of
regimes over time, lifecycle patterns of regimes, proportion of lifecycle
regimes and downtime between regimes. Armed
with these parameters he determined the lowest and highest values of L.
According to Charles Rubin, L is among the hardest to quantify on the
basis of empirical information. This
has led to conflicting assumptions about the lifespan of civilisations that tend
to reflect “the hopes and fears about the human future” he said.
Tough called for widening the range of search strategies, while Jill Tarter
provided a roadmap for future SETI observing projects up to the year 2020 based
on a series of workshops held at the SETI Institute. She identified three different approaches, viz: continue the
radio search with an affordable array built from consumer market components and
an increase in the target list to 100 000 stars, begin searches for very fast
optical and infrared pulses from a million stars and build an omni-directional
sky survey array for detecting radio signals from billions of stars.
According to her, “SETI could succeed tomorrow or it may be an
endeavour for multiple generations. When
our use of the spectrum becomes more efficient, it will be time to consider
deliberate transmissions and the really tough questions: Who will speak for
Earth? What will they say?
Maybe by then we will be old enough to find some answers”.
up the baton for Optical SETI, Stuart Kingsley gave the delegates an historical
overview of where Optical SETI had come from since 1961.
He also speculated on the “eventual need to move Optical SETI
observations into space with high altitude balloons and space-based
Chairman’s review paper on Optical SETI Observatories in the New Millennium
is extensively hyperlinked and is available for download in both PDF and HTML
present day OSETI searches were described by Paul Horowitz
(Harvard-Smithsonian), Dan Wertheimer (University of California Berkeley),
Shelley Wright (Lick Observatory) and Ragbir Bhathal (OZ OSETI Project).
All four projects are searching for nanosecond laser pulses from ETI
civilisations in coincidence mode. Horowitz
also described the Planetary Society sponsored new All-Sky Survey OSETI project
his group is undertaking. According
to him, a dedicated 1.8 m f/2.4 spherical glass light bucket and an array of
pixelated photomultipliers will be deployed in transit mode to cover the
northern sky in about 150 nights. Bhathal
described his use of two telescopes placed about 20 meters apart for his Optical
SETI project. His instrumentation
set up eliminates most of the extraneous signals which seem to plague the other
OSETI experiments. His is the only
dedicated southern hemisphere Optical SETI project.
Howard informed the delegates of some of the interference problems that OSETI
searches have to contend with. He
examined the astrophysical, atmospheric, terrestrial and instrumental sources of
optical pulses that need to be considered as ‘RFI’ for pulsed Optical SETI.
Werthimer gave the delegates an overview of his radio and Optical SETI
programs which include SETI@Home, SERENDIP and
SEVENDIP. The SERENDIP IV sky
survey searches for narrow band signals in ‘piggyback’ mode on the 305-meter
Arecibo Observatory at Puerto Rico. The
new SEVENDIP Optical SETI search looks for ETI signals from F, G and K stars,
plus a few globular clusters and galaxies.
Shelley Wright described an improved Optical SETI receiver, which uses a
three-detector system rather than two detectors as used by the other groups.
It will be mounted on the Lick Observatory’s one-meter Nickel
reflector. Corbin Covault discussed
the rather interesting possibility of using the large collecting area of the
National Solar Thermal Test Facility for Optical SETI.
It has 200 fully trackable mirrors (called heliostats), each providing 37
square metres of collecting area. At
present it is used at night for gamma-ray astronomy. Robert Bradbury provided a retrospective view of Dyson
shells. He also gave an update of
the concept of Dyson shells, which included our current knowledge of
biotechnology, nanotechnology and computer science.
search for probes is an alternative search strategy for searching for ETI.
Scott Stride noted that there is instrument technology available today to
carry out a search for interstellar robotic probes.
According to him, “Autonomous instrument platforms (robotic
observatories) to search for anomalous energy signatures can be designed and
assembled using commercial off-the-shelf (COTS) sensors, hardware and embedded
computer processing speed necessary to establish a nearby ETI probe detection of
interest”. Allen Tough informed
delegates that in widening the search strategy he had established the
‘Invitation to ETI’ on the World Wide Web to enable a small super smart
autonomous robot probe to make contact with the 80 persons included on his list.
Shuch spoke of the need to recognise the work of the amateur SETI community.
The SETI League's Argus Sky Survey, he said was “carrying out credible
science with modest amateur equipment” although “many traditional radio
astronomers still believe that SETI requires the kind of facilities that only
governments can afford”. Monte
Ross outlined an Optical SETI project, which could involve amateur astronomers
on a massive scale. According to
him, the PhotonStar Project is “an enterprise to detect extraterrestrial laser
signals that involves many individual small telescopes acting together as a
geographically diverse large array, which together comprise a large collection
area and thereby offer a better chance of detection if signals exist”.
alternative method of searching for life on other planets is to find other
Earths. Ron Bracewell described his
highly innovative nulling interferometry method of imaging nonsolar planets.
The basic idea according to Bracewell “is to adjust an interferometer
for a null in its median plane so as to null out the radiation received from the
star, and to spin the interferometer about the earth-star line to gain the
signal-to-noise improvement associated with phase-sensitive detection”.
Since his initial idea a number of improvements have been made to his
concept. The nulling principle has
been demonstrated to work without going to space.
The results of a number of experiments have provided important inputs to
NASA's Terrestrial Planet Finder mission. Oswald
Wallner discussed the nulling capability of space-based interferometers and the
extreme requirements for interferometer uniformity.
Steve Kilston took the delegates on a tour of the next generation of
space telescopes and discussed the possibilities of space-based Optical SETI.
According to him, the Next-Generation-Space Telescope (NGST), the
Terrestrial Planet Finder (TPF), and Darwin (IRSI) were particularly useful for
SETI searches at optical wavelengths. The
new space observatories, he said, offered a number of capabilities, which would
be of interest to SETI researchers. These
were: calibrated instruments for continuous extended time observing a particular
planetary system, sensitivity in wavelength regions which were difficult to
observe through the earth's atmosphere, very high photometric accuracy to detect
small variations in signal from a planetary system, decreased scattered light
from our solar system's zodiacal light and the potential of blocking (nulling)
most of a star’s light thereby making it easier to detect light from objects
close to the star.
stressed the importance of SETI education in both formal and non-formal
educational settings. He described
a number of projects that are taking place at the university level, the school
level and for the general public. However,
the most successful public program to date has been the SETI@Home
program run by Werthimer. According
to Werthimer, over 2.5 million people worldwide are involved with the SETI@Home
project. It is, he said “the
largest supercomputer on the planet, currently averaging 20 Teraflops”.
search for extraterrestrial intelligence is a unique scientific activity.
However, it has yet to come to grips with its philosophical foundations
and needs to clearly demarcate itself from UFO and other fringe studies.
In his paper, Arthur Fricke explored the SETI hypothesis with respect to
Karl Popper and Paul Feyerabend’s philosophies of science.
question of communication with ETI was the subject of Brian McConnell's paper. A number of strategies have been proposed for communicating
with ETI. However, these can
roughly be divided into two categories, viz: pictorial and mathematical systems.
According to McConnell, it is also “possible to construct a complex
message by using algorithms as a foundation upon which a rich symbolic
vocabulary can be built”. Brian
McConnell also has a great new SETI book out Beyond Contact: A Guide to SETI
and Communicating with Alien Civilizations.
Amongst its other attributes, this is the first book to give a good
account of Optical SETI.
an open panel discussion towards the end of the conference, Douglas Vakoch
raised the question of a protocol for discovery and contact for researchers
working in the field of OSETI. A
number of views were expressed as to the desirability of having a protocol for
OSETI. Horowitz was not in favour
of this as he felt that it was demeaning to the whole enterprise.
He believed that there were sufficient safeguards and checks in normal
science to ensure that the OSETI experiments followed the strict guidelines for
good science. It was also pointed out that Optical SETI as opposed to
Microwave SETI would have a large following because there were already large
numbers of amateur optical astronomers world wide.
Once the cost of the instrumentation and some of the problems associated
with the searches were ironed out, it would be possible to carry out the
extensive type of PhotonStar project that was outlined by Ross and Kingsley.
chairs acknowledge the financial assistance of SPIE and the Laser Space Signals
Observatory (LSSO) for providing the funds to bring Professor Chandra
Wickramasinghe from the United Kingdom. We also wish to thank Doug Vakoch for moderating and
summarizing the workshop. The
date for the next Optical SETI conference has not been set, but because this
field of research is set to see very dynamic growth over the coming decade, we
expect that OSETI IV will be held before 2005.
those of you who could not make it to this conference, PowerPoint, RealAudio and
some RealVideo clips of the presentations and workshop will, in time, be
available on the COSETI Web site,
as well as links to other materials on the individual Web sites of the various
Stuart A. Kingsley and Dr. Ragbir Bhathal
Chairs and Editors
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