PROCEEDINGS VOLUME 4273The Search for Extraterrestrial Intelligence (SETI) in the Optical Spectrum III Editor(s): Stuart A. Kingsley; Ragbir Bhathal
*This item is only available on the SPIE Digital Library.
Volume Number: 4273Date Published: 3 August 2001
Table of Contents show all abstracts | hide all abstracts Unity of cosmic life and the inevitability of evolved life forms
Author(s): Nalin Chandra Wickramasinghe; Fred Hoyle Show Abstract The concept of life being a cosmic phenomenon is rapidly gaining support, with new evidence from space science, geology and biology. On this picture life on Earth resulted from the introduction of bacteria from comets and the subsequent evolution of life required the continuing input of genes from comets. By analogy, the case for similar evolutionary developments elsewhere in the universe is explored. The prospects for SETI and Optical SETI are examined in relation to the theory of panspermia. Panspermia asks new questions
Author(s): Brig Klyce Show Abstract There is a widespread sentiment that panspermia is uninteresting is because it does not answer fundamental questions about the origin of life. The strongest version of panspermia asks entirely new questions. While barriers to the acceptance of panspermia are falling and evidence supporting it is accumulating, the mere possibility of panspermia unhinges the Darwinian account of evolutionary progress. The new theory removes an issue dividing science and religion, but it requires an amendment to the big bang theory. Can terrestrial planets exist in the habitable zones of known exoplanetary systems?
Author(s): Barrie W. Jones; P. Nick Sleep Show Abstract The habitable zone (HZ) is defined as the range of distances from a star within which water at the surface of a terrestrial planet would be in the liquid phase. We have investigated whether terrestrial planets could exit in the HZs of known exoplanetary systems long enough for life to have emerged and to have evolved. Four contrasting systems in which giant planets have been detected have been examined, and HZs have been defined for each system using conservative definitions for the HZ boundaries. Mixed- variable sympletic numerical integration has ben used to investigate the orbits of putative terrestrial planets launched within the HZ of each system. In Rho CrB the HZ is exterior to the giant, and in 47 UMa it is interior. We have shown that in each of these two systems terrestrial planets could have orbits with semimajor axes that remain confined to the HZ for biologically significant lengths of time. We have also shown that the Gliese 876 and Ups And systems are very unlikely to have such orbits. Optical SETI observatories in the new millennium: a review
Author(s): Stuart A. Kingsley Show Abstract The Optical Search for Extraterrestrial Intelligence is now 40 years old. However, it was only during the closing years of the 20th Century, after a 25-year hiatus, that the optical search has regained respectability in the SETI community at large. The quarter-of-a-century delay in American Optical SETI research was due to a historical accident and not for the lack of any enabling technology. This review paper describes aspects of past, present and future Optical SETI programs. Emphasis is placed on detecting fast, pulsed attention-getting laser beacon signals rather than monochromatic, continuous wave beacons. Some examples of commercial detection equipment that may be employed for either type of OSETI are given. Berkeley radio and optical SETI programs: [email protected], SERENDIP, and SEVENDIP
Author(s): Dan Werthimer; David Anderson; C. Stuart Bowyer; Jeff Cobb; Eric Heien; Eric J. Korpela; Michael L. Lampton; Matt Lebofsky; Geoff W. Marcy; Meghan McGarry; Dick Treffers Show Abstract We present results from two radio and two optical SETI programs at the University of California, Berkeley: The SERENDIP IV sky survey searches for narrow band radio signals at the 305 meter Arecibo Observatory in Puerto Rico. The program uses a 168 million channel spectrum analyser, running in 'piggyback' mode, using a dedicated receiver to take data 24 hours a day, year round. SETIhome is Berkeley's most recent SETI project. SETIhome uses desktop computers of over a million volunteers to analyse 40 Terabytes of data from Arecibo Observatory. SETIhome is the largest supercomputer on the planet, currently averaging 20 Teraflops. The SEVENDIP optical program searches for nS timescale pulses at visible wavelengths. The target list includes nearby F,G,K and M stars, plus a few globular cluster and galaxies. The pulse search utilizes Berkeley's 30 inch automated telescope at Leuschner Observatory. Another Berkeley optical SETI program searches for narrow band coherent signals in high resolution stellar spectra taken by Marcy and his colleagues as part of their on-going search for planets at Lick, Keck, and the Anglo-Australian observatories. PhotonStar project
Author(s): Monte Ross; Stuart A. Kingsley Show Abstract The PhotonStar SETI 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, thereby, offering a better chance of detection if signals exist. Widely separated small telescopes, each with a sensitive photon detection capability, can be aimed simultaneously at the same star system with precise timing that enables looking at the same time for short pulse detection. Each individual telescope can be located via GPS so that the differential distance from the star compared to every other telescope can be determined beforehand. Coordination via the Internet would enable each telescope to operate as one element of the array. This project allows direct public participation by amateur astronomers into the search for extraterrestrial intelligence as there are thousands of telescopes of eight inches or greater in use, so that the total collection area can be very substantial with public participation. In this way, each telescope is part of a larger array with data being sent via the Internet to a central station. This approach is only feasible now with the advent of GPS, the Internet, and relatively low- cost single photon detector technology. Imaging nonsolar planets by nulling interferometry
Author(s): Ronald N. Bracewell Show Abstract The Large Binocular Telescope, comprising two 8.4 m mirrors spaced 14.4 m between centers on a single altazimuth mount, will allow further experience with nulling interferometry on a large scale. The housing on Mt Graham, Arizona, is ready to receive the telescope structure, which has been prefabricated in Italy. Philosophical perspectives on the problem of extraterrestrial signal detection
Author(s): Arthur C. Fricke Show Abstract SETI (the Search for Extra-Terrestrial Intelligence) is a unique scientific activity. Given that SETI researchers purport to study a phenomenon that has as of yet not been demonstrated to exist, some commentators claim that the field cannot in fact be called 'scientific' at all. Examining the field from a philosophical perspective, this paper will show that SETI does indeed satisfy Popperian falsificationist principles of scientific legitimacy. In addition, this paper will highlight how these principles apply to methodological diversity within SETI. SETI 2020: a roadmap for future SETI observing projects
Author(s): Jill C. Tarter Show Abstract A recent series of workshops has laid out a roadmap for SETI research at the SETI Institute for the next few decades. Three different approaches were identified. 1) Continue the radio search: build an affordable array incorporating consumer market technologies, expand the search frequency, and increase the target list to 100,000 stars. This array will also serve as a technology demonstration and enable the international radio astronomy community to realize an array that is a hundred times larger and capable (among other things) of searching a million stars. 2) Begin searches for very fast optical pulses from a million stars. 3) As Moore's Law delivers increased computational capacity, build an omni-directional sky survey array capable of detecting strong, transient, radio signals from billions of stars. SETI could succeed tomorrow, or it may be an endeavor for multiple generations. We are a very young technology in a very old galaxy. While our own leakage radiation continues to outshine the Sun at many frequencies, we remain detectable to others. 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? Widening the range of search strategies
Author(s): Allen Tough Show Abstract From 1960 until 1998, the scientific search for extraterrestrial intelligence relied primarily on a single strategy: (1) using radio telescopes to find an artificial signal from many light-years away. In 1998, the field expanded its array of search strategies from one primary strategy to three by adding optical SETI and solar system SETI. Each of these three current major strategies has a good chance of success. (2) Optical SETI uses optical telescopes to find a pulsed laser message or some other artificial signal from many light-years away. This approach has several advantages. It is covered thoroughly at Stuart Kingsley's www.coseti.org website and was discussed extensively at this conference. (3) The third current strategy is solar system SETI. This is an effort to detect irrefutable scientific evidence of any highly advanced intelligence that has reached out planet or somewhere else in the solar system. Extraterrestrial civilizations and their technology are likely thousands of years older and more advanced than ours. Consequently, they could send a small super-smart autonomous robot probe to explore our planet and monitor our telecommunications. To make contact with such a probe, about 80 SETI scientists and others have placed an invitation to ETI on the World Wide Web. Factors affecting calculation of L
Author(s): Mark P.A. Ciotola Show Abstract A detectable extraterrestrial civilization can be modeled as a series of successive regimes over time each of which is detectable for a certain proportion of its lifecycle. This methodology can be utilized to produce an estimate for L. Potential components of L include quantity of fossil fuel reserves, solar energy potential, quantity of regimes over time, lifecycle patterns of regimes, proportion of lifecycle regime is actually detectable, and downtime between regimes. Relationships between these components provide a means of calculating the lifetime of communicative species in a detectable state, L. An example of how these factors interact is provided, utilizing values that are reasonable given known astronomical data for components such as solar energy potential while existing knowledge about the terrestrial case is used as a baseline for other components including fossil fuel reserves, quantity of regimes over time, and lifecycle patterns of regimes, proportion of lifecycle regime is actually detectable, and gaps of time between regimes due to recovery from catastrophic war or resource exhaustion. A range of values is calculated for L when parameters are established for each component so as to determine the lowest and highest values of L. roadmap for SETI research at the SETI Institute for the next few decades. Three different approaches were identified. 1) Continue the radio search: build an affordable array incorporating consumer market technologies, expand the search frequency, and increase the target list to 100,000 stars. This array will also serve as a technology demonstration and enable the international radio astronomy community to realize an array that is a hundred times larger and capable (among other things) of searching a million stars. 2) Begin searches for very fast optical pulses from a million stars. 3) As Moore's Law delivers increased computational capacity, build an omni-directional sky survey array capable of detecting strong, transient, radio signals from billions of stars. SETI could succeed tomorrow, or it may be an endeavor for multiple generations. We are a very young technology in a very old galaxy. While our own leakage radiation continues to outshine the Sun at many frequencies, we remain detectable to others. 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? Targeted and all-sky search for nanosecond optical pulses at Harvard-Smithsonian
Author(s): Paul Horowitz; Charles M. Coldwell; Andrew B. Howard; David W. Latham; Robert Stefanik; Jonathan Wolff; Joe M. Zajac Show Abstract We have built a system to detect nanosecond pulsed optical signals from a target list of some 10,000 sun-like stars, and have made some 20,000 observations during its two years of operation. A beamsplitter feeds a pair of hybrid avalanche photodetectors at the focal plane of the 1.5m Cassegrain at the Harvard/Smithsonian Oak Ridge Observatory (Agassiz Station), with a coincidence triggering measurement of pulse width and intensity at sub-nanosecond resolution. A flexible web-enabled database, combined with mercifully low background coincidence rates (approximately 1 event per night), makes it easy to sort through far-flung data in search of repeated events from any candidate star. An identical system will soon begin observations, synchronized with ours, at the 0.9m Cassegrain at Princeton University. These will permit unambiguous identification of even a solitary pulse. We are planning an all-sky search for optical pulses, using a dedicated 1.8m f/2.4 spherical glass light bucket and an array of pixelated photomultipliers deployed in a pair of matched focal planes. The sky pixels, 1.5 arcmin square, tessellate a 1.6 by 0.2 degree patch of sky in transit mode, covering the Northern sky in approximately 150 clear nights. Fast custom IC electronics will monitor corresponding pixels for coincident optical pulses of nanosecond timescale, triggering storage of a digitized waveform of the light flash. Optical SETI comes of age
Author(s): H. Paul Shuch Show Abstract Recent pioneering efforts in microwave Search for Extra- Terrestrial Intelligence (SETI) have met with similar resistance from the established SETI community, reminding one of an adage from the American West: pioneers end up with arrows in their backs. The SETI League's Project Argus sky survey, for example, which seeks to do credible science with modest amateur equipment, designed, built and operated by dedicated non-professionals, continues to draw criticism from the SETI establishment. Many traditional radio astronomers still believe that SETI requires the kinds of facilities which only governments can afford. This paper explores optical SETI's recent move from the sidelines to center stage, in search of lessons which the world's amateur microwave SETIzens can learn from our dedicated optical brethren. Next-generation space telescope (NGST) and space-based optical SETI
Author(s): Steven Kilston; David L. Begley Show Abstract Many new space observatory projects are now being discussed and planned. With the primary goals of useful astronomical research, including detection and characterization of extrasolar planetary systems, the larger of such prospective observatories include the Next-Generation Space Telescope (NGST), Terrestrial Planet Finder (TPF), Darwin, Life Finder (LF), and Planet Imager (PI). Several of these seem particularly useful for SETI searches at optical wavelengths, as do also some smaller proposed space observatories such as Eclipse, Kepler, and GAIA. The new space observatories offer the following capabilities of particular interest to SETI: (1) single, calibrated instruments providing continuous extended time observing a particular planetary system or a wide-angle region containing many possible systems; (2) sensitivity in wavelength regions difficult to observe through the earth's atmosphere due to absorption or to scattered light; (3) very high photometric accuracy to detect small variations in signal from a planetary system; (4) decreased scattered light from our solar system's zodiacal light, depending on observatory orbit location; and (5) the potential of blocking (nulling) most of a star's light, thereby increasing greatly the signal-to-noise ratio (SNR) for detecting light from objects close to the star. We offer some suggestions as to how these new space observatories might be employed or adapted to offer optical SETI capabilities, and provide estimates of their potential performance for that mission. Optical SETI in Australia
Author(s): Ragbir Bhathal Show Abstract This paper discusses and describes one of the new optical search strategies that have come on-line in the last few years. Armed with a $DLR250,000 optical SETI observatory built mainly through private sector funds and other off- campus telescopes the OZ OSETI Project is searching for very fast optical pulses beamed at planet Earth by Extraterrestrial Intelligence civilizations which have surpassed the radio threshold. The search has initially concentrated on southern circumpolar stars and globular clusters. Is there RFI in pulsed optical SETI?
Author(s): Andrew B. Howard; Paul Horowitz Show Abstract In the 40 year history of SETI, radio frequency interference (RFI) has proven to be the dominant background in microwave searches. As the SETI community broadens its electromagnetic scope and searches for optical beacons, it must characterize and identify backgrounds for pulsed optical SETI. We must ask the question: What is the ``RFI'' for pulsed optical SETI? This paper seeks to answer the question by examining the astrophysical, atmospheric, terrestrial, and instrumental sources of optical pulses of nanosecond timescale. Potential astrophysical/atmospheric sources include airglow and scattered zodiacal light, stellar photon pileup, muon events, and cosmic-ray induced Cerenkov flashes. Terrestrial sources, including lightning and laser communications, appear negligible. Instrumental backgrounds such as scintillation in detector optics and corona breakdown have been the dominant background in our experiments to date, and present significant design challenges for future optical SETI researchers. New OSETI observatory to search for interstellar probes
Author(s): Eamonn Ansbro Show Abstract Numerous researchers have suggested the importance of including a near-Earth search for interstellar probes in the search for extraterrestrial intelligence. This paper documents some of the scientific work that has already been undertaken in this field and my own intended contributions. The research under discussion includes both the theoretical and the practical. Overview of laser communications research at JPL
Author(s): Hamid Hemmati Show Abstract NASA is currently building a 1-m R&D telescope laboratory at its Table Mountain Facility in southern California to answer key implementation questions of this technology. The telescope is designed with fast tracking capability and will act as a testbed for development of ground acquisition, tracking and communication strategies applicable to future operational stations. Establishment of requirements and analysis to predict the performance of large diameter `photon bucket' telescope is continuing. These and other programs currently under development are described below. Instrument technologies for the detection of extraterrestrial interstellar robotic probes
Author(s): Scot L. Stride Show Abstract In the continuing endeavor to detect evidence of ETI (Extraterrestrial Intelligence) in the solar neighborhood, instrument technologies now exist that allow the formation of a scientific method to carry out a search for interstellar robotic probes of possible extraterrestrial origin. The range of currently observable probe features/manifestations will be shown and how they influence search space, instrument selection and deployment. Autonomous instrument platforms (i.e. robotic observatories) to search for anomalous energy signatures can be designed and assembled using Commercial off-the-shelf (COTS) hardware and software. The COTS approach to observatory design provides an economical, flexible and robust path toward collecting reliable data. The present variety of COTS instruments permits the necessary observational sensitivity, bandwidth and embedded processing speed to establish a nearby robotic probe detection envelope. A survey of these instrument technologies will be presented and how they can be applied to the challenge of collecting enough scientific data on anomalous observational phenomena to determine whether or not a robotic probe was detected. Dyson shells: a retrospective
Author(s): Robert J. Bradbury Show Abstract More than 40 years have passed since Freeman Dyson suggested that advanced technological civilizations are likely to dismantle planets in their solar systems to harvest all of the energy their stars wastefully radiate into space. Clearly this was an idea that was ahead of its time. Since that time, dozens of SETI searches have been conducted and almost all of them have focused their attention on stars which by definition cannot be the advanced civilizations that Dyson envisioned. I will review the data that created the confusion between Dyson spheres and Dyson shells. The sources that disprove Dyson spheres while still allowing Dyson shells will be discussed. The use of outmoded ideas that have biased the few searches for Dyson Shells that have occurred will be pointed out. An update of the concept of Dyson shells to include our current knowledge of biotechnology, nanotechnology and computer science will be explored. Finally, an approach to setting limits on the abundance of Dyson shells in our galaxy using existing optical astronomical data and future optical satellites will be proposed. Large area solar power heliostat array for OSETI
Author(s): Corbin E. Covault Show Abstract Current OSETI programs make use of optical telescopes with light collection areas on the order of 10 square meters or less. The small collection area limits the ultimate sensitivity achievable to low-intensity signals. However, solar power facilities such as the National Solar Thermal Test Facility (NSTTF) provide the potential for a much larger collecting area. The NSTTF is operated at by the Department of Energy at Sandia National Laboratories for research in solar power development and testing. The NSTTF site includes over 200 fully steerable mirrors (called heliostats) each providing 37 square meters of collecting area. This facility is currently being used at night for gamma-ray astronomy. The STACEE experiment makes use of 64 heliostats to detect nanosecond flashes of optical Cherenkov light associated with gamma-ray air showers from the top of the atmosphere. The STACEE experiment has been in operation since 1998 and has already detected gamma-rays from the Crab Nebula. In principle, the STACEE experiment can be operated with minor modifications to detect OSETI signals on the ground at a photon density of less than two optical photons per square meter per pulse. We summarize performance results from the STACEE experiment, and we discuss the sensitivity of a hypothetical future STACEE-OSETI experiment with particular attention to potential sources of background. Nulling interferometry for spectroscopic investigation of exoplanets: a statistical analysis of imperfections
Author(s): Oswald Wallner; Klaus H. Kudielka; Walter R. Leeb Show Abstract In ESA's Infrared Space Interferometry mission, a multi-aperture interferometer fed by telescopes will serve to analyse exoplanets orbiting bright stars. Spectroscopy of the planet's radiation could give hints on the possibility of the existence of life. However, for a Sun/Earth-like constellation, a star light rejection ratio of some 80 dB is required. This is the factor by which the star light is suppressed, when comparing the interferometer with a standard, wide-field-of-view telescope. We investigate the nulling capability of space-based interferometers, realized either in fiber or bulk optics, in the presence of imperfections of the structure and of optical components. Mismatch of amplitude, optical path length, and polarization among the interferometer arms is taken into account, as well as multiple reflections and telescope imperfections. The parameters describing the interferometer's receive characteristic, which are actively controlled or influenced by environmental disturbances, are modeled stochastically. We analyse Sun/Earth-like constellations by numerical simulation for a wavelength range of 6 to 18 microns. The expected value of the star light rejection ratio is calculated for several interferometer configurations. The exemplary numerical results confirm the extreme requirements for interferometer uniformity and give a quantitative insight into the dependence of the attainable rejection ratio on individual and/or combined interferometer imperfections. Improved optical SETI detector
Author(s): Shelley A. Wright; Frank Drake; Remington P.S. Stone; Dick Treffers; Dan Werthimer Show Abstract Two-detector optical SETI systems have experienced a surprising incidence of false positive signals. We describe a three-detector system designed to alleviate this difficulty. The device will be mounted on Lick Observatory's 1-meter Nickel reflector. Algorithmic communication with extraterrestrial intelligence (ACETI)
Author(s): Brian McConnell Show Abstract Many different strategies for communication with extraterrestrial intelligence have been proposed since the invention of wireless communication. these strategies can be roughly divided into two categories: pictorial and non- pictorial (math-based) systems. Pictorial messages, such as the bitmap transmitted from the Arecibo radiotelescope in 1975, can be used to communicate a wide variety of ideas and symbols. Non-pictorial systems, such as Hans Freudenthal's language Lingua Cosmica (Lincos), allow the sender to build a symbolic vocabulary without the use of pixelated images. Life at the limits of physical laws
Author(s): Robert J. Bradbury Show Abstract Some of the problems that plague SETI research are the problems of the abundance of liquid water planets, the probability of the development of intelligent life, whether or not intelligent life forms develop technology, how long intelligent technological civilizations may survive, and whether or not interstellar travel or colonization are feasible or affordable. These problems lead to extensive and potentially irresolvable debates regarding the various paths species and civilizations may follow from a primitive level to our current level and beyond. This discussion will focus instead on the question of what the characteristics of intelligent technological life should be at the limits of known physical laws. Why do this? Well, because as Scotty observed on the Starship Enterprise, ``Captain, I canna change the laws of physics the laws of physics do not deny the feasibility of a life form, the lack of a practical engineering path to it may prevent its existence. At these limits, the form(s) that life takes may be clearer because convergent evolution could drive civilizations into a very limited set of ecological niches. An architecture for civilizations that hits many of these limits will be proposed. Its 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. Such civilizations, should, over time, become the dominant population of galaxies. Our own civilization may reach this state within this century. The impact of these conclusions on classical radio and optical SETI verses astrometric and occultation astronomy will be discussed. L factor: hope and fear in the search for extraterrestrial intelligence
Author(s): Charles T. Rubin Show Abstract The L factor in the Drake equation is widely understood to account for most of the variance in estimates of the number of extraterrestrial intelligences that might be contacted by the search for extraterrestrial intelligence (SETI). It is also among the hardest to quantify. An examination of discussions of the L factor in the popular and technical SETI literature suggests that attempts to estimate L involve a variety of potentially conflicting assumptions about civilizational lifespan that reflect hopes and fears about the human future. Evidence for biomarkers and microfossils in ancient rocks and meteorites
Author(s): Richard B. Hoover; Alexei Yu. Rozanov Show Abstract We review prior studies of chemical and morphological biomarkers in ancient rocks and meteorites and present recently obtained ESEM images of microfossils and nanofossils in-situ in freshly fractured surfaces of Nogoya and pristine samples of Murchison as further evidence of indigenous microfossils in meteorites. Formal and nonformal SETI education programs
Author(s): Ragbir Bhathal Show Abstract Frank Drake's experiment on the search for extraterrestrial intelligence in 1960 not only generated a new field of observational astronomy but also produced spin-offs in the fields of education and the social science. SETI education programs in formal and non-formal educational institutions provide a powerful tool for educating the public and students about humanity's most profound question: are we alone in the universe? This paper discusses SETI educational programs in both formal and non-formal settings.