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All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

The SETI instrument development plan

The architecture of the instrument system for the SETI (Search for Extraterrestrial Intelligence) program is briefly described and the development approach used to implement the operational instruments is discussed. The two versions of the instrument system include a target survey instrument to observe at a very high sensitivity a selected set of interesting stars that have particular a priori promise, and a sky survey instrument to observe the entire celestial sphere at a lower sensitivity. The targeted survey utilizes the 305 meter antenna at Arecibo, Puerto Rico, a 64 meter DSN antenna, and other large radio telescopes. The Arecibo instrument provides the highest sensitivity by virtue of the antenna gain. The antenna line feeds cover an instantaneous frequency range of 50 MHz (tunable over 100 MHz), while the multichannel spectrum analyzer/signal detector is capable of analyzing a frequency segment 16 MHz wide with a maximum resolution of 1 Hz. The sky survey employs a listen-only, 34 meter antenna. The SETI breadboard development is also described.

Crow, R. B.↗
NASA NTRS1980

Analysis of SETI data collected in the parasitic mode

A system for performing SETI observations continuously as part of non-SETI observations at a radio observatory is presented, and the analysis of results obtained by the parasitic system is discussed. The system, designated SERENDIP, is a real-time microprocessor-controlled spectrum analyzer with algorithms for performing statistical operations and recording those spectra with characteristics presumed to be typical of intelligent rather than astrophysical origin. Programs also exist for the post-acquisition analysis of signal autocorrelation, power spectra, time behavior and positional coordinates, and for a generalized cluster analysis to detect clusters of signal detections. In a recent run of 35 days, the SERENDIP system detected 4000 narrowband spectra exceeding a preset threshold, of which 98% were determined to be of instrumental origin. The remaining class of detections is also believed to be instrumental, although not as well organized as the first signals, and means are currently being sought for eliminating them.

Bowyer, S.↗
NASA NTRS1982

SETI downconverter

The SETI (Search for Extraterrestrial Intelligence) breadboard subsystem was begun in order to develop the technology to efficiently implement a SETI instrument capable of searching wide bandwidth with high resolution. The downconverter covered is the interface hardware between the receiver IF output and ADC used as the input to the spectrum analyzer.

Crow, B.↗
NASA NTRS1983

The Berkeley parasitic SETI program

Parasitic programs for the Search for Extraterrestrial Intelligence (SETI), carried out concurrently with conventional radio astronomical observing programs, can be an attractive and cost-effective means of exploring the large multidimensional search space intrinsic to this effort. A microprocessor-based automated SETI acquisition system is described which searches for, and records, spectra of narrowband signals in the IF band of an observatory receiver. Data taken with this system over 35 days at the Hat Creek Radio Observatory at 1612 MHz are discussed. Out of approximately 100,000 spectra processed during this period, 4000 were identified by the system as containing narrowband signals and were recorded. Subsequent analysis indicates that over 3900 of these are due to local RF contamination. The remainder are undergoing further investigation.

Bowyer, S.↗
NASA NTRS1985

SETI radio spectrum surveillance system

The SETI Radio Spectrum Surveillance System (SRSSS) will provide a data base for assessing the radio frequency interference (RFI) environment for SETI and minimizing RFI disruptions during the search. The system's hardware and software are described and the sensitivity of the system is discussed.

Crow, B.↗
NASA NTRS1985

Objectives and first results of the NASA SETI Sky Survey field tests at Goldstone, California

The objectives and preliminary results of the initial field tests of the prototype hardware and software for the NASA SETI program are reviewed with emphasis on the Sky Survey component of the NASA search strategy. In particular, attention is given to field test instrumentation, sky pixelation, sky survey field tests, baseline tests, antenna control tests, and radio frequency interference survey. The test results and observational experience will be used to finalize the design of the SETI Sky Survey processing system and to optimize the observational strategy and procedures in time to begin a full-scale Microwave Observing Program in 1990.

Gulkis, S.↗
NASA NTRS1985

SETI - A more eclectic approach

NASA's proposed search for extraterrestrial intelligence (SETI) program is discussed. The receiving antennas and search strategy for SETI are described. The use of a multichannel spectrum analyzer which resolves 8 MHz of spectrum into 8 million individual channels is examined. The CW and pulse detection procedures are analyzed.

Oliver, B. M.↗
NASA NTRS1985

SETI - The microwave search problem and the targeted search approach

The targeted search component of the NASA SETI program is limited to time sharing in the usual fashion on existing large radio telescopes. Unless the consequences of this restriction are compensated by increased capability in the SETI electronic systems, an undesirable loss in sensitivity must be accepted in order to prevent a more costly and humanly unattractive lengthening of the projected five-year observing program to a duration of some decades.

Seeger, C. L.↗
NASA NTRS1986

A SETI experiment

In order to increase the probability of contact in the search for extraterrestrial intelligence (SETI), it has been proposed to search more intensively in certain regions of the electromagnetic spectrum ('the water hole'). The present paper describes a similar narrowing of the search in the time domain. Application of this strategy results in the SETI experiments searching for signals from the Tau Ceti system late in 1986 and early in 1987, and from the Epsilon Eridani system in mid 1988.

Mclaughlin, W. I.↗
NASA NTRS1986

Objectives and first results of the NASA SETI sky survey field tests at Goldstone

Field tests of SETI (Search for Extraterrestrial Intelligence) prototype hardware and software began in March 1985 at Goldstone. With emphasis on the sky survey component of the NASA SETI search strategy, the article describes the survey characteristics, the detection strategy, and preliminary results of system tests.

Gulkis, S.↗
NASA NTRS1986

Analysis of a crossed Bragg-cell acousto optical spectrometer for SETI

The search for radio signals from extraterrestrial intelligent (SETI) beings requires the use of large instantaneous bandwidth (500 MHz) and high resolution (20 Hz) spectrometers. Digital systems with a high degree of modularity can be used to provide this capability, and this method has been widely discussed. Another technique for meeting the SETI requirement is to use a crossed Bragg-cell spectrometer as described by Psaltis and Casasent (1979). This technique makes use of the Folded Spectrum concept, introduced by Thomas (1966). The Folded Spectrum is a two-dimensional Fourier Transform of a raster scanned one-dimensional signal. It is directly related to the long one-dimensional spectrum of the original signal and is ideally suited for optical signal processing.

Gulkis, S.↗
NASA NTRS1986

The NASA SETI program - An overview

The development and objectives of the NASA SETI program are reviewed. The search strategy for the program is two phase, an all-sky survey and a targeted search; the capabilities and hardware for the searches are discussed. The use of a spectrum analyzer to search the GHz of the spectrum, and of a multichannel spectrum analyzer to detect pulses are examined; the designs and functions of the analyzers are described. A new method for detecting a drifting CW signal is proposed. A diagram of the automated SETI system is presented.

Oliver, Bernard M.↗
NASA NTRS1989

Pulsar-aided SETI experimental observations

The rotational frequencies of pulsars are used to select preferred radio frequencies for SETI. Pulsar rotational frequencies are converted into SETI frequencies in the 1-10 GHz Galactic radio window. Experimental observations using the frequencies are conducted for target stars closer than 25 parsecs, unknown targets in a globular cluster, and unknown targets in the Galaxy closer than 2.5 kpc. The status of these observations is discussed.

Heidmann, J.↗
NASA NTRS1989

Detection of the earth with the SETI microwave observing system assumed to be operating out in the Galaxy

The maximum range is calculated at which radar signals from the earth could be detected by a search system similar to the NASA SETI 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 planned to be operating in the 1990s. The probability of detection is calculated for the two most powerful transmitters, the planetary radar at Arecibo (Puerto Rico) and the ballistic missile early warning systems (BMEWSs), assuming that the terrestrial radars are only in the eavesdropping mode. It was found that, for the case of a single transmitter within the maximum range, the highest probability is for the sky survey detecting BMEWSs; this is directly proportional to BMEWS sky coverage and is therefore 0.25.

Billingham, John↗
NASA NTRS1990

Exobiology and SETI from the lunar farside

Within the Life Sciences Division of NASA, the Exobiology Program seeks to understand the origin, evolution and distribution of life in the universe. There are two feasible methods of searching for life beyond the earth. The first is to return to Mars and systematically explore its surface and subsurface with instrumentation capable of identifying extinct as well as extant life. The second is to search for advanced forms of life in other planetary systems that have developed a technology capable of modifying their environment in ways that make it detectable across the vast interstellar distances. The Exobiology Program is currently pursuing both of these options. If NASA's SETI (search for extraterrestrial intelligence) Microwave Observing Project of the 1990s fails to detect evidence of radio signals generated by an extraterrestrial technology, what might be the next step? The establishment of a permanent lunar base early in the next century may enable the construction of large aperture radio telescopes that can extend both the sensitivity and the frequency range of SETI observations. A lunar base may also provide the opportunity for construction of optical and IR telescopes intended for the direct detection of extrasolar planetary systems.

Tarter, Jill C.↗
NASA NTRS1991

The NASA SETI program

In 1959, it was proposed that a sensible way to conduct interstellar communication would be to use radio at or near the frequency of hydrogen. In 1960, the first Search for Extraterrestrial Intelligence (SETI) was conducted using a radiotelescope at Green Bank in West Virginia. Since 1970, NASA has systematically developed a definitive program to conduct a sophisticated search for evidence of extraterrestrial intelligent life. The basic hypothesis is that life may be widespread in the univers, and that in many instances extraterrestrial life may have evolved into technological civilizations. The underlying scientific arguments are based on the continuously improving knowledge of astronomy and astrophysics, especially star system formation, and of planetary science, chemical evolution, and biological evolution. If only one in a million sun-like stars in our galaxy harbors species with cognitive intelligence, then there are 100,000 civilizations in the Milky Way alone. The fields of radioastronomy digital electronic engineering, spectrum analysis, and signal detection have advanced rapidly in the last twenty years and now allow for sophisticated systems to be built in order to attempt the detection of extraterrestrial intelligence signals. In concert with the scientific and engineering communities, NASA has developed, over the last several years, a Microwave Observing Project whose goal is to design, build, and operate SETI systems during the decade of the nineties in pursuit of the goal signal detection. The Microwave Observing Project is now approved and underway. There are two major components in the project: the Target Search Element and the Sky Survey Element.

Billingham, J.↗
NASA NTRS1991

NASA-SETI microwave observing project: Targeted Search Element (TSE)

The Targeted Search Element (TSE) performs one of two complimentary search strategies of the NASA-SETI Microwave Observing Project (MOP): the targeted search. The principle objective of the targeted search strategy is to scan the microwave window between the frequencies of one and three gigahertz for narrowband microwave emissions eminating from the direction of 773 specifically targeted stars. The scanning process is accomplished at a minimum resolution of one or two Hertz at very high sensitivity. Detectable signals will be of a continuous wave or pulsed form and may also drift in frequency. The TSE will possess extensive radio frequency interference (RFI) mitigation and verification capability as the majority of signals detected by the TSE will be of local origin. Any signal passing through RFI classification and classifiable as an extraterrestrial intelligence (ETI) candidate will be further validated at non-MOP observatories using established protocol. The targeted search will be conducted using the capability provided by the TSE. The TSE provides six Targeted Search Systems (TSS) which independently or cooperatively perform automated collection, analysis, storage, and archive of signal data. Data is collected in 10 megahertz chunks and signal processing is performed at a rate of 160 megabits per second. Signal data is obtained utilizing the largest radio telescopes available for the Targeted Search such as those at Arecibo and Nancay or at the dedicated NASA-SETI facility. This latter facility will allow continuous collection of data. The TSE also provides for TSS utilization planning, logistics, remote operation, and for off-line data analysis and permanent archive of both the Targeted Search and Sky Survey data.

Webster, L. D.↗
NASA NTRS1991

The SERENDIP 2 SETI project: Current status

Over the past 30 years, interest in extraterrestrial intelligence has progressed from philosophical discussion to rigorous scientific endeavors attempting to make contact. Since it is impossible to assess the probability of success and the amount of telescope time needed for detection, Search for Extraterrestrial Intelligence (SETI) Projects are plagued with the problem of attaining the large amounts of time needed on the world's precious few large radio telescopes. To circumvent this problem, the Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations (SERENDIP) instrument operates autonomously in a piggyback mode utilizing whatever observing plan is chosen by the primary observer. In this way, large quantities of high-quality data can be collected in a cost-effective and unobtrusive manner. During normal operations, SERENDIP logs statistically significant events for further offline analysis. Due to the large number of terrestrial and near-space transmitters on earth, a major element of the SERENDIP project involves identifying and rejecting spurious signals from these sources. Another major element of the SERENDIP Project (as well as most other SETI efforts) is detecting extraterrestrial intelligence (ETI) signals. Events selected as candidate ETI signals are studied further in a targeted search program which utilizes between 24 to 48 hours of dedicated telescope time each year.

Bowyer, C. S.↗