SPIE's OSETI III Conference (No. 4273)

The Search for Extraterrestrial Intelligence (SETI)
in the Optical Spectrum III

Preface

In 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.[1]  This was followed by a second conference in 1996, which was held in San Jose.  The keynoter then was Professor Ron Bracewell.[2]  The third conference this year was again held in San Jose with the keynote address being given by Professor Chandra Wickramasinghe.[3]  SPIE’s OSETI III conference celebrated the 40^th 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.

The 3^rd 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 journal.

For 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.

Four 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 civilisations.

Early 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 Sydney.

There 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.

The 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 extremophiles survive. 

Andy 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 civilization.       

The 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.  

Allen 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”.

Taking 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 telescopes”.  The 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 formats.[4]

Individual 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. 

Andrew 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.

The 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.

Paul 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”.

Another 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.       

Bhathal 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”.

The 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.

The 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.[5]  Amongst its other attributes, this is the first book to give a good account of Optical SETI.

In 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.

The 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.  For 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[6], as well as links to other materials on the individual Web sites of the various authors.

Dr. Stuart A. Kingsley[7] and Dr. Ragbir Bhathal[8]

Conference Chairs and Editors

May 30, 2001

• Introductory remarks from the OSETI I Conference

• Introductory remarks from the OSETI II Conference