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All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Computational problems and signal processing in SETI

The Search for Extraterrestrial Intelligence (SETI), currently being planned at NASA, will require that an enormous amount of data (on the order of 10 exp 11 distinct signal paths for a typical observation) be analyzed in real time by special-purpose hardware. Even though the SETI system design is not based on maximum entropy and Bayesian methods (partly due to the real-time processing constraint), it is expected that enough data will be saved to be able to apply these and other methods off line where computational complexity is not an overriding issue. Interesting computational problems that relate directly to the system design for processing such an enormous amount of data have emerged. Some of these problems are discussed, along with the current status on their solution.

Deans, Stanley R.↗
NASA NTRS1992

Detection of the Earth with the SETI microwave observing system assumed to be operating out in the galaxy

This paper estimates the maximum range at which radar signals from the Earth could be detected by a search system similar to the NASA Search for Extraterrestrial Intelligence Microwave Observing Project (SETI MOP) assumed to be operating out in the galaxy. Figures are calculated for the Targeted Search, and for the Sky Survey parts of the MOP, both operating, as currently planned, in the second half of the decade of the 1990s. Only the most powerful terrestrial transmitters are considered, namely, the planetary radar at Arecibo in Puerto Rico, and the ballistic missile early warning systems (BMEWS). In each case the probabilities of detection over the life of the MOP are also calculated. The calculation assumes that we are only in the eavesdropping mode. Transmissions intended to be detected by SETI systems are likely to be much stronger and would of course be found with higher probability to a greater range. Also, it is assumed that the transmitting civilization is at the same level of technological evolution as ours on Earth. This is very improbable. If we were to detect another technological civilization, it would, on statistical grounds, be much older than we are and might well have much more powerful transmitters. Both factors would make detection by the NASA MOP a much more likely outcome.

NASA Center ARC↗
NASA NTRS2016

A Search for Brief Optical Flashes Associated with the SETI Target KIC 8462852

The F-type star KIC8462852 has recently been identified as an exceptional target for search for extraterrestrial intelligence (SETI) observations. We describe an analysis methodology for optical SETI, which we have used to analyze nine hours of serendipitous archival observations of KIC8462852 made with the VERITAS gamma-ray observatory between 2009 and 2015. No evidence of pulsed optical beacons, above a pulse intensity at the Earth of approximately 1 photon/sq m, is found. We also discuss the potential use of imaging atmospheric Cherenkov telescope arrays in searching for extremely short duration optical transients in general.

astrobiology – extraterrestrial intelligence –↗
NASA NTRS1978

The SETI Radio Observational Project - Strategy, instrumentation, and objectives

The paper describes strategies, tradeoffs, instrumentation, and overall objectives for the SETI Radio Observation Project. Novel approaches have been formulated in order to achieve coverage of the desirable frequency and spatial regimes (about 80% of the sky and in the frequency range of 1.4-25 GHz). A mixed strategy has been developed which uses the survey capability of small antennas and the sensitivity of modern maser amplifiers to achieve sensitivities comparable to those reached by previous observers, but with as much as 10,000 times the scope of both the frequency and spatial coverage possible to those experimenters.

Edelson, R. E.↗
NASA NTRS1980

The SETI observational plan

The SETI (Search for Extraterrestrial Intelligence) Project's primary thrust is to search the microwave region of the spectrum for signals of extraterrestrial intelligent origin. The project will search a well defined volume of search parameter space using existing antennae and a sophisticated data acquisition and analysis system. Two major components are included, the target survey, which will observe at very high sensitivity all attractive stellar candidates within 75 light years of the Sun, and the sky survey, which will observe the entire celestial sphere at a lower sensitivity.

Berman, A. L.↗
NASA NTRS1980

A bimodal search strategy for SETI

The search strategy and resultant observational plan which was developed to carry out a comprehensive Search for Extraterrestrial Intelligence (SETI) over that portion of the electromagnetic spectrum known as the terrestrial microwave window is described. The limiting sensitivity achieved was parameterized and calculated for Deep Space Network antennas as well as several radio astronomy observatories. A brief description of the instrumentation to be employed in the search and the classes of signals to be looked for is given. One observational goal is to survey the entire sky over a wide range of frequency to a relatively constant flux level. This survey ensures that all potential life sites are observed to some limiting equivalent isotropic radiated power depending upon their distance. A second goal is to survey a set of potential transmission sites selected a priori to be especially promising, achieving very high sensitivity over a smaller range of frequency.

Gulkis, S.↗
NASA NTRS1980

A bimodal search strategy for SETI

A SETI plan has been developed jointly by the NASA Ames Research Center and the Jet Propulsion Laboratory with the objective of both observing all potential sites to some limiting equivalent isotropic radiated power and surveying with greater sensitivity a set of especially promising sites. The bimodal search strategy assumes that existing radio telescopes with state-of-the-art receivers and data processing devices will have the sensitivity to explore the vicinity of nearby stars for similar transmitters and the entire galaxy for more powerful signals. The discrete source observational mode is designed to observe 773 F, G and K-type stars within 25 pc of the sun at frequencies from 1.2 to 3 GHz and spot bands between 3 and 25 GHz with sensitivities from 10 to the -25th to 10 to the -27th W/sq m. The sky survey is intended to search the entire celestial sphere between 1.2 and 10 GHz and spot bands between 10 and 25 GHz at a sensitivity limit of approximately 10 to the -23rd times the square root of the frequency. Instrumentation for the surveys includes a large multichannel spectrum analyzer. Immediate goals of the program are the investigation of the RF background at high resolution and the development of signal detection algorithms, with operation to begin in 1984.

Gulkis, S.↗
NASA NTRS1981

A dedicated 26-m SETI sky survey instrument facility: A feasibility study

The feasibility of converting a deactivated GSTDN 26 m facility into a dedicated SETI Instrument Facility is examined. Additional benefits that would accrue from the proposed utilization of these facilities are the capability for remote and control the Deep Space Communications Complex (DSCC) Signal Processing Center, combined with a reduction in ground-induced radio frequency interference due to the physical distance to the other DSCC front end areas and the Signal Processing Center.

Berman, A. L.↗
NASA NTRS1983

SETI Pulse Detection Algorithm: Analysis of False-alarm Rates

Some earlier work by the Search for Extraterrestrial Intelligence (SETI) Science Working Group (SWG) on the derivation of spectrum analyzer thresholds for a pulse detection algorithm based on an analysis of false alarm rates is extended. The algorithm previously analyzed was intended to detect a finite sequence of i periodically spaced pulses that did not necessarily occupy the entire observation interval. This algorithm would recognize the presence of such a signal only if all i-received pulse powers exceeded a threshold T(i): these thresholds were selected to achieve a desired false alarm rate, independent of i. To simplify the analysis, it was assumed that the pulses were synchronous with the spectrum sample times. This analysis extends the earlier effort to include infinite and/or asynchronous pulse trains. Furthermore, to decrease the possibility of missing an extraterrestrial intelligence signal, the algorithm was modified to detect a pulse train even if some of the received pulse powers fall below the threshold. The analysis employs geometrical arguments that make it conceptually easy to incorporate boundary conditions imposed on the derivation of the false alarm rates. While the exact results can be somewhat complex, simple closed form approximations are derived that produce a negligible loss of accuracy.

Levitt, B. K.↗
NASA NTRS1984

SETI Investigations at Jodrell Bank, England: September Through November 1983

The radiofrequency interference RFI environment was examined in the frequency band 1404 to 1444 MHz using the DSN Advanced Systems' Radio Frequency Interference Surveillance System. An uncooled FET amplifier was placed on the 12.8-m antenna, and unlimited observing time was made available to the SETI project. One night of observing at 1667 MHz was made available on the 76 m antenna. Preliminary results of four investigations are reported: (1) full scans of the horizon, cataloging RFI events between 1404 and 1444 MHz; (2) lunar reflections of terrestrial RFI signals between 1424 and 1444 MHz; (3) noise background distortions caused by galactic neutral hydrogen emission at 1420.4 MHz; and (4) low sensitivity search for spectral features of F, G, and K stars.

Downs, G. S.↗
NASA NTRS1983

The NASA SETI Program - Objectives of the R&D activity

The current activity in NASA's SETI Program is a research and development program jointly carried out by the NASA Ames Research Center and the Jet Propulsion Laboratory. The purpose of this R&D phase is to develop all prerequisites for a well defined microwave observing program. The specific objectives include the development of a prototype search system which will ultimately be capable of processing data rates up to 10 gigabytes/second. Specialized signal detection algorithms and automated search procedures will be developed and tested with the prototype hardware. A series of field tests will be carried out with the NASA Deep Space Network facilities at Goldstone, CA and with the 305-m radio telescope at the Arecibo Ionospheric Observatory in Puerto Rico.

Klein, M. J.↗
NASA NTRS1985

A signal detection strategy for the SETI All Sky Survey

A source detection strategy for the SETI All Sky Survey is described. The method is designed to detect continuous wave (or very narrowband) sources transitting an antenna beam. The short-time spectra of the received signal are accumulated, and candidate extraterrestrial sources are recognized by the recognized by the presence of narrowband power exceeding a threshold function. The threshold function is derived using a Neyman-pearson hypothesis test.

Lawton, W.↗
NASA NTRS1986

Time and space integrating acousto-optic folded spectrum processing for SETI

Time and space integrating folded spectrum techniques utilizing acousto-optic devices (AOD) as 1-D input transducers are investigated for a potential application as wideband, high resolution, large processing gain spectrum analyzers in the search for extra-terrestrial intelligence (SETI) program. The space integrating Fourier transform performed by a lens channels the coarse spectral components diffracted from an AOD onto an array of time integrating narrowband fine resolution spectrum analyzers. The pulsing action of a laser diode samples the interferometrically detected output, aliasing the fine resolution components to baseband, as required for the subsequent charge coupled devices (CCD) processing. The raster scan mechanism incorporated into the readout of the CCD detector array is used to unfold the 2-D transform, reproducing the desired high resolution Fourier transform of the input signal.

Wagner, K.↗
NASA NTRS1986

Overview of the NASA SETI Program

The NASA Search of Extraterrestrial Intelligence (SETI) program plan is to scan the microwave window from 1 to 10 GHz with existing radio telescopes and sophisticated signal processing equipment looking for narrow band features that might represent artificial signals. A microwave spectrometer was built and is being field tested. A pattern recognition computer to search for drifting continuous wave signals and pulse trains in the output spectra is being designed. Equipment to characterize the radio frequency interference environment was also built. The plan is to complete the hardware and software by FY-88. Then, with increased funding, this equipment will be replicated in Very Large Scale Integration form. Observations, both a complete sky survey and a search fo nearby solar type stars, will begin in about 1990. The hypothesis that very powerful signals exist or that signals are being beamed at us will be tested. To detect the kinds of signals radiated at distances of 100 light years will require a collecting area kilometers in diameter.

Oliver, B. M.↗
NASA NTRS1985

The Ohio SETI program - The first decade

A full-time dedicated SETI program has been in operation at Ohio State University since 1973. A 50-channel narrowband filter bank is in use near the 21 cm hydrogen-line. All data is processed in real time and permanently recorded. A large portion of the northern sky has been surveyed and analyzed for large-scale structure. The only obvious nonrandom structure is caused by isolated narrowband pulses, which are anticorrelated with galactic latitude, and congregate in two specific areas. The origin of these pulses is unknown, although they may be partially due to instrumental effects.

Dixon, R. S.↗
NASA NTRS1985

SETI - The microwave search problem and the NASA sky survey approach

NASA's microwave observing program for SETI is presented. This strategy is composed of a high sensitivity, narrow frequency coverage, Target Search and a low sensitivity, broad frequency coverage, Sky Survey. The complementary nature of this dual mode search strategy is discussed. An overview is given of ongoing work in the development of the search strategy for the Sky Survey.

Klein, M. J.↗
NASA NTRS1986

Risk and value analysis of SETI

The risks, values, and costs of the SETI project are evaluated and compared with those of the Viking project. Examination of the scientific values, side benefits, and costs of the two projects reveal that both projects provide equal benefits at equal costs. The probability of scientific and technical success is analyzed.

Billingham, J.↗
NASA NTRS1986

The NASA SETI program at JPL

The NASA All Sky Survey strategy for detecting signals of extraterrestrial origin is examined. The All Sky Survey observes the entire celestial sphere, covers a frequency range of 1-10 Ghz, and has spatial direction and frequency coverage. The survey time is dependent on the area of the sky surveyed, the telescope diameter, scan rate, the angular separation of the scans, the bandwidth of the receiver, and the frequency coverage. The distance at which a transmitter can be detected for a given sensitivity is analyzed. The interaction between scan strategy and various accumulation strategies and its effect on the sensitivity of the survey are investigated using field tests. A diagram of the SETI Sky Survey observational system is provided.

Gulkis, Sam↗