We report radio SETI observations on a large number of known exoplanets and other nearby star sys... more We report radio SETI observations on a large number of known exoplanets and other nearby star systems using the Allen Telescope Array (ATA). Observations were made over about 19000 hr from 2009 May to 2015 December. This search focused on narrowband radio signals from a set totaling 9293 stars, including 2015 exoplanet stars and Kepler objects of interest and an additional 65 whose planets may be close to their habitable zones. The ATA observations were made using multiple synthesized beams and an anticoincidence filter to help identify terrestrial radio interference. Stars were observed over frequencies from 1 to 9 GHz in multiple bands that avoid strong terrestrial communication frequencies. Data were processed in near-real time for narrowband (0.7-100 Hz) continuous and pulsed signals with transmitter/receiver relative accelerations from −0.3 to 0.3 m s −2. A total of 1.9 × 10 8 unique signals requiring immediate follow-up were detected in observations covering more than 8 × 10 6 star-MHz. We detected no persistent signals from extraterrestrial technology exceeding our frequency-dependent sensitivity threshold of 180-310 × 10 −26 W m −2 .
The Rio scale is a tool for communicating the significance of a signal to the general public. It ... more The Rio scale is a tool for communicating the significance of a signal to the general public. It assigns scores to signals detected in searches for extraterrestrial intelligence (SETI), which characterizes both the consequences of a signal and the probability the signal is truly from ETI, in an easily digestible format for laypeople to interpret. In the 17 years since its construction, the number of groups actively conducting searches for evidence of intelligent life beyond the Earth has increased significantly, and theoretical work has established a new suite of observables that are capable of revealing the presence of ETI in a range of astronomical observations. In this paper, we revise the Rio scale, with the aim of (i) achieving consensus across academic disciplines on a scheme for classifying signals potentially indicating the existence of advanced extraterrestrial life, (ii) supplying a pedagogical tool to help inform the public about the process scientists go through to devel...
Submitted as a white paper to the National Academies of Sciences, Engineering, and Medicine ad ho... more Submitted as a white paper to the National Academies of Sciences, Engineering, and Medicine ad hoc Committee on Astrobiology Science Strategy for Life in the Universe, National Research Council, Washington, DC, 2018. Summary: Not knowing exactly what to look for, Astrobiology should embrace, and prioritize, all scientifically plausible and technologically feasible search strategies for both biosignatures and technosignatures. There is no scientific justification for excluding SETI, or any other technosignature modality, from the suite of astrobiological investigations. Arguments based on political sensitivities or apparent access to other funding sources are inappropriate. In this white paper, we argue for a level playing field.
Fifty years ago Giuseppe Cocconi and Philip Morrison [1] ended their Nature paper with the senten... more Fifty years ago Giuseppe Cocconi and Philip Morrison [1] ended their Nature paper with the sentence “The probability of success is difficult to estimate, but if we never search, the chance of success is zero”, and thereby launched a new exploratory science known as SETI – the search for extraterrestrial intelligence. Today SETI falls under the umbrella of astrobiology, a suite of cross-disciplinary sciences attempting to understand the origin, nature, and distribution of life in the cosmos. Astrobiology enjoys a substantial enthusiasm among researchers despite the fact that no compelling evidence for life beyond Earth has yet been found. New technologies and observatories offer extraordinary potential for major astrobiological finds and young scientists are wagering with their careers. Few topics in astronomy or astrobiology generate as much interest and excitement as SETI. It is still not possible to estimate with any accuracy the chances of success; but the discovery of extrasolar...
The Allen Telescope Array was used to search for signals with characteristics similar to the “Wow... more The Allen Telescope Array was used to search for signals with characteristics similar to the “Wow” signal, the best candidate for an extraterrestrial radio signal found during Ohio State University’s (OSU’s) seven-year 21 cm 10-kHz channel sky survey for signals possibly due to extraterrestrial intelligence. While previous follow-up searches have reported null results, our observations covered a 5 deg2 field of view that extends well beyond the locus of all consistent directions of arrival (DOAs) of the original signal, and covered a 10 MHz bandwidth four times wider than the widest prior follow-up observations, using 12.8 kHz channels approximating OSU’s 10 kHz resolution. Approximately 100 hours of data were accumulated, considerably more time than any previous follow-up campaigns. We used interferometric imaging with an angular resolution of approximately 007 and automated feature-finding to search for point-like features mimicking a Wow repetition, obtaining single-channel sensi...
Dr. Sofia Sheikh moderated this panel about how to get involved in SETI, featuring Dr. Steve Crof... more Dr. Sofia Sheikh moderated this panel about how to get involved in SETI, featuring Dr. Steve Croft, Dr. Cherry Ng, Dr. Jill Tarter, and Prof. Jason Wright.
The search for extraterrestrial intelligence (SETI) could succeed tomorrow, decades from now, or ... more The search for extraterrestrial intelligence (SETI) could succeed tomorrow, decades from now, or never. The nature of this scientific exploration is such that we cannot predict success on any timescale; we only know that if we do not search, we cannot succeed. Having spent my scientific career in this field, I know perhaps better than anyone that the researchers of
We present our second paper on the Allen Telescope Array Twenty-centimeter Survey (ATATS), a mult... more We present our second paper on the Allen Telescope Array Twenty-centimeter Survey (ATATS), a multi-epoch, ∼ 700 square degree radio image and catalog at 1.4 GHz. The survey is designed to detect rare, bright transients as well as to commission the ATA's wide-field survey capabilities. ATATS explores the challenges of multi-epoch transient and variable source surveys in the domain of dynamic range limits and changing (u, v) coverage. Here we present images made using data from the individual epochs, as well as a revised image combining data from all ATATS epochs. The combined image has RMS noise σ = 3.96 mJy beam −1 , with a circular beam of 150 FWHM. The catalog, generated using a false detection rate algorithm, contains 4984 sources, and is > 90% complete to 37.9 mJy. The catalogs generated from snapshot images of the individual epochs contain between 1170 and 2019 sources over the 564 square degree area in common to all epochs. The 90% completeness limits of the single epoch catalogs range from 98.6 to 232 mJy. We compare the catalog generated from the combined image to those from individual epochs, and from the NRAO VLA Sky Survey (NVSS), a legacy survey at the same frequency. We are able to place new constraints on the transient population: fewer than 6 × 10 −4 transients deg −2 , for transients brighter than 350 mJy with characteristic timescales of minutes to days. This strongly rules out an astronomical origin for the ∼ 1 Jy sources reported by Matsumura et al. (2009), based on their stated rate of 3.1 × 10 −3 deg −2 .
In order to conduct a systematic microwave search for extraterrestrial intelligence (SETI), NASA ... more In order to conduct a systematic microwave search for extraterrestrial intelligence (SETI), NASA is planning to use an advanced multichannel spectrum analyzer (MCSA) capable of resolving the input bandwidth into at least 10 million narrowband channels. To verify the digital architecture that NASA is proposing to use to construct such an instrument, a 74000 channel prototype, the MCSA 1.0, has been built and deployed in the field. This paper discusses the results of the field tests, implications for other components of an automated SETI observing system, and plans to use the MCSA 1.0 to carry out some more traditional radio astronomy observations.
The Search for ExtraTerrestrial Intelligence (SETI) finally has its own full-time telescope. The ... more The Search for ExtraTerrestrial Intelligence (SETI) finally has its own full-time telescope. The Allen telescope array (ATA) in Northern California was dedicated on October 11, 2007. This array, which will eventually be composed of 350 small radio antennas, each 6.1 m in diameter, is being built as a partnership between the SETI Institute and the University of California Radio Astronomy Laboratory. Last October, Paul G. Allen (who provided the funds for the technology development and the first phase of array construction) pushed a silver button and all 42 antennas of the current ATA-42 slewed to point in the direction of the distant galaxy M81. Specialized electronic backend detectors attached to the ATA began making a radio map of that galaxy and simultaneously began SETI observations of HIP48573, a G5V star near M81 on the sky and a distance of 264 light years from Earth. The Allen telescope array will greatly improve the speed of conducting SETI searches over the next few decades, and it will allow a suite of different search strategies to be undertaken. This paper summarizes some of the earliest SETI observations from the array, and describes the search strategies currently being planned.
In August, 1981, the Westerbork Synthesis Radio Telescope was used for 4 h to search for narrowba... more In August, 1981, the Westerbork Synthesis Radio Telescope was used for 4 h to search for narrowband pulsing radio beacons in the direction of the Galactic Center. By using both the spatial discrimination and temporal stability available to an interferometric measurement, weak intermittent signals can be detected even in the face of the strong, naturally caused radiation from this region. A radio beacon within our bandwidth, centered on the 21 cm neutral hydrogen line, would be recognizable if it had a repetition period between 40 sec and 1/2 h. The rms sensitivity to point sources was approximately 50 mJy/cycle, and the detection limit was 500 mJy/cycle. The limit degrades for pulse widths < 0.02s. No repetitive signals were found. For a swept, narrow-band radio beacon constrained to the Galactic Disk (beamwidth = 0.02 rad), our detection limit corresponds to a transmitter power of 10(11) MW at the Galactic Center.
The Ad Hoc Committee on SETI Nomenclature was convened at the suggestion of Frank Drake after the... more The Ad Hoc Committee on SETI Nomenclature was convened at the suggestion of Frank Drake after the Decoding Alien Intelligence Workshop at the SETI Institute in March 2018. The purpose of the committee was to recommend standardized definitions for terms, especially those that are used inconsistently in the literature and the scientific community. The committee sought to recommend definitions and terms that are a compromise among several desirable but occasionally inconsistent properties for such terms: 1) Consistency with the historical literature and common use in the field; 2) Consistency with the present literature and common use in the field; 3) Precision of meaning; 4) Consistency with the natural (i.e. everyday, non-jargon) meanings of terms; 5) Compatibility with non-English terms and definitions. The definitions in this report are restricted to technical, SETI contexts, where they may have jargon senses different from their everyday senses. In many cases we include terms only...
Numerous small reflector antennas, with cost-effective electronics, feed information into this te... more Numerous small reflector antennas, with cost-effective electronics, feed information into this telescope, designed to search for extraterrestrial intelligence and produce images covering wide areas of the sky.
We report radio SETI observations on a large number of known exoplanets and other nearby star sys... more We report radio SETI observations on a large number of known exoplanets and other nearby star systems using the Allen Telescope Array (ATA). Observations were made over about 19000 hr from 2009 May to 2015 December. This search focused on narrowband radio signals from a set totaling 9293 stars, including 2015 exoplanet stars and Kepler objects of interest and an additional 65 whose planets may be close to their habitable zones. The ATA observations were made using multiple synthesized beams and an anticoincidence filter to help identify terrestrial radio interference. Stars were observed over frequencies from 1 to 9 GHz in multiple bands that avoid strong terrestrial communication frequencies. Data were processed in near-real time for narrowband (0.7-100 Hz) continuous and pulsed signals with transmitter/receiver relative accelerations from −0.3 to 0.3 m s −2. A total of 1.9 × 10 8 unique signals requiring immediate follow-up were detected in observations covering more than 8 × 10 6 star-MHz. We detected no persistent signals from extraterrestrial technology exceeding our frequency-dependent sensitivity threshold of 180-310 × 10 −26 W m −2 .
The Rio scale is a tool for communicating the significance of a signal to the general public. It ... more The Rio scale is a tool for communicating the significance of a signal to the general public. It assigns scores to signals detected in searches for extraterrestrial intelligence (SETI), which characterizes both the consequences of a signal and the probability the signal is truly from ETI, in an easily digestible format for laypeople to interpret. In the 17 years since its construction, the number of groups actively conducting searches for evidence of intelligent life beyond the Earth has increased significantly, and theoretical work has established a new suite of observables that are capable of revealing the presence of ETI in a range of astronomical observations. In this paper, we revise the Rio scale, with the aim of (i) achieving consensus across academic disciplines on a scheme for classifying signals potentially indicating the existence of advanced extraterrestrial life, (ii) supplying a pedagogical tool to help inform the public about the process scientists go through to devel...
Submitted as a white paper to the National Academies of Sciences, Engineering, and Medicine ad ho... more Submitted as a white paper to the National Academies of Sciences, Engineering, and Medicine ad hoc Committee on Astrobiology Science Strategy for Life in the Universe, National Research Council, Washington, DC, 2018. Summary: Not knowing exactly what to look for, Astrobiology should embrace, and prioritize, all scientifically plausible and technologically feasible search strategies for both biosignatures and technosignatures. There is no scientific justification for excluding SETI, or any other technosignature modality, from the suite of astrobiological investigations. Arguments based on political sensitivities or apparent access to other funding sources are inappropriate. In this white paper, we argue for a level playing field.
Fifty years ago Giuseppe Cocconi and Philip Morrison [1] ended their Nature paper with the senten... more Fifty years ago Giuseppe Cocconi and Philip Morrison [1] ended their Nature paper with the sentence “The probability of success is difficult to estimate, but if we never search, the chance of success is zero”, and thereby launched a new exploratory science known as SETI – the search for extraterrestrial intelligence. Today SETI falls under the umbrella of astrobiology, a suite of cross-disciplinary sciences attempting to understand the origin, nature, and distribution of life in the cosmos. Astrobiology enjoys a substantial enthusiasm among researchers despite the fact that no compelling evidence for life beyond Earth has yet been found. New technologies and observatories offer extraordinary potential for major astrobiological finds and young scientists are wagering with their careers. Few topics in astronomy or astrobiology generate as much interest and excitement as SETI. It is still not possible to estimate with any accuracy the chances of success; but the discovery of extrasolar...
The Allen Telescope Array was used to search for signals with characteristics similar to the “Wow... more The Allen Telescope Array was used to search for signals with characteristics similar to the “Wow” signal, the best candidate for an extraterrestrial radio signal found during Ohio State University’s (OSU’s) seven-year 21 cm 10-kHz channel sky survey for signals possibly due to extraterrestrial intelligence. While previous follow-up searches have reported null results, our observations covered a 5 deg2 field of view that extends well beyond the locus of all consistent directions of arrival (DOAs) of the original signal, and covered a 10 MHz bandwidth four times wider than the widest prior follow-up observations, using 12.8 kHz channels approximating OSU’s 10 kHz resolution. Approximately 100 hours of data were accumulated, considerably more time than any previous follow-up campaigns. We used interferometric imaging with an angular resolution of approximately 007 and automated feature-finding to search for point-like features mimicking a Wow repetition, obtaining single-channel sensi...
Dr. Sofia Sheikh moderated this panel about how to get involved in SETI, featuring Dr. Steve Crof... more Dr. Sofia Sheikh moderated this panel about how to get involved in SETI, featuring Dr. Steve Croft, Dr. Cherry Ng, Dr. Jill Tarter, and Prof. Jason Wright.
The search for extraterrestrial intelligence (SETI) could succeed tomorrow, decades from now, or ... more The search for extraterrestrial intelligence (SETI) could succeed tomorrow, decades from now, or never. The nature of this scientific exploration is such that we cannot predict success on any timescale; we only know that if we do not search, we cannot succeed. Having spent my scientific career in this field, I know perhaps better than anyone that the researchers of
We present our second paper on the Allen Telescope Array Twenty-centimeter Survey (ATATS), a mult... more We present our second paper on the Allen Telescope Array Twenty-centimeter Survey (ATATS), a multi-epoch, ∼ 700 square degree radio image and catalog at 1.4 GHz. The survey is designed to detect rare, bright transients as well as to commission the ATA's wide-field survey capabilities. ATATS explores the challenges of multi-epoch transient and variable source surveys in the domain of dynamic range limits and changing (u, v) coverage. Here we present images made using data from the individual epochs, as well as a revised image combining data from all ATATS epochs. The combined image has RMS noise σ = 3.96 mJy beam −1 , with a circular beam of 150 FWHM. The catalog, generated using a false detection rate algorithm, contains 4984 sources, and is > 90% complete to 37.9 mJy. The catalogs generated from snapshot images of the individual epochs contain between 1170 and 2019 sources over the 564 square degree area in common to all epochs. The 90% completeness limits of the single epoch catalogs range from 98.6 to 232 mJy. We compare the catalog generated from the combined image to those from individual epochs, and from the NRAO VLA Sky Survey (NVSS), a legacy survey at the same frequency. We are able to place new constraints on the transient population: fewer than 6 × 10 −4 transients deg −2 , for transients brighter than 350 mJy with characteristic timescales of minutes to days. This strongly rules out an astronomical origin for the ∼ 1 Jy sources reported by Matsumura et al. (2009), based on their stated rate of 3.1 × 10 −3 deg −2 .
In order to conduct a systematic microwave search for extraterrestrial intelligence (SETI), NASA ... more In order to conduct a systematic microwave search for extraterrestrial intelligence (SETI), NASA is planning to use an advanced multichannel spectrum analyzer (MCSA) capable of resolving the input bandwidth into at least 10 million narrowband channels. To verify the digital architecture that NASA is proposing to use to construct such an instrument, a 74000 channel prototype, the MCSA 1.0, has been built and deployed in the field. This paper discusses the results of the field tests, implications for other components of an automated SETI observing system, and plans to use the MCSA 1.0 to carry out some more traditional radio astronomy observations.
The Search for ExtraTerrestrial Intelligence (SETI) finally has its own full-time telescope. The ... more The Search for ExtraTerrestrial Intelligence (SETI) finally has its own full-time telescope. The Allen telescope array (ATA) in Northern California was dedicated on October 11, 2007. This array, which will eventually be composed of 350 small radio antennas, each 6.1 m in diameter, is being built as a partnership between the SETI Institute and the University of California Radio Astronomy Laboratory. Last October, Paul G. Allen (who provided the funds for the technology development and the first phase of array construction) pushed a silver button and all 42 antennas of the current ATA-42 slewed to point in the direction of the distant galaxy M81. Specialized electronic backend detectors attached to the ATA began making a radio map of that galaxy and simultaneously began SETI observations of HIP48573, a G5V star near M81 on the sky and a distance of 264 light years from Earth. The Allen telescope array will greatly improve the speed of conducting SETI searches over the next few decades, and it will allow a suite of different search strategies to be undertaken. This paper summarizes some of the earliest SETI observations from the array, and describes the search strategies currently being planned.
In August, 1981, the Westerbork Synthesis Radio Telescope was used for 4 h to search for narrowba... more In August, 1981, the Westerbork Synthesis Radio Telescope was used for 4 h to search for narrowband pulsing radio beacons in the direction of the Galactic Center. By using both the spatial discrimination and temporal stability available to an interferometric measurement, weak intermittent signals can be detected even in the face of the strong, naturally caused radiation from this region. A radio beacon within our bandwidth, centered on the 21 cm neutral hydrogen line, would be recognizable if it had a repetition period between 40 sec and 1/2 h. The rms sensitivity to point sources was approximately 50 mJy/cycle, and the detection limit was 500 mJy/cycle. The limit degrades for pulse widths < 0.02s. No repetitive signals were found. For a swept, narrow-band radio beacon constrained to the Galactic Disk (beamwidth = 0.02 rad), our detection limit corresponds to a transmitter power of 10(11) MW at the Galactic Center.
The Ad Hoc Committee on SETI Nomenclature was convened at the suggestion of Frank Drake after the... more The Ad Hoc Committee on SETI Nomenclature was convened at the suggestion of Frank Drake after the Decoding Alien Intelligence Workshop at the SETI Institute in March 2018. The purpose of the committee was to recommend standardized definitions for terms, especially those that are used inconsistently in the literature and the scientific community. The committee sought to recommend definitions and terms that are a compromise among several desirable but occasionally inconsistent properties for such terms: 1) Consistency with the historical literature and common use in the field; 2) Consistency with the present literature and common use in the field; 3) Precision of meaning; 4) Consistency with the natural (i.e. everyday, non-jargon) meanings of terms; 5) Compatibility with non-English terms and definitions. The definitions in this report are restricted to technical, SETI contexts, where they may have jargon senses different from their everyday senses. In many cases we include terms only...
Numerous small reflector antennas, with cost-effective electronics, feed information into this te... more Numerous small reflector antennas, with cost-effective electronics, feed information into this telescope, designed to search for extraterrestrial intelligence and produce images covering wide areas of the sky.
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