&lt;title&gt;Is there RFI in pulsed optical SETI?&lt;/title&gt;

Howard, Andrew; Horowitz, Paul

doi:10.1117/12.435369

Cited by 8 publications

(3 citation statements)

References 14 publications

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“…While there is no natural background at these frequencies except the 3 K CMB, radio searches must expend significant computing resources to mitigate the effects of human-caused RFI, and giving up pieces of some spectral bands altogether, even at the quietest sites. At optical frequencies, signals exhibiting extreme time compression (broadband laser pulses) are searched for with photon counters having nanosecond rise times, a regime with no known sources of astrophysical background (Howard & Horowitz 2001). Because interstellar dust begins to absorb optical pulses over distances beyond ∼ 1000 ly, it is desirable to extend the optical SETI search into the infrared so that more of the Galaxy becomes accessible.…”

Section: Exploring the Cosmic Haystackmentioning

confidence: 99%

The evolution of life in the Universe: are we alone?

Tarter

2006

Proc. IAU

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Abstract. In his book Plurality of Worlds, Steven J. Dick (1984) has chronicled the millennia of discourse about other inhabited worlds, based upon deeply held religious or philosophical belief systems. The popularity of the idea of extraterrestrial life has waxed and waned and, at its nadir, put proponents at mortal risk. The several generations of scientists now attending this General Assembly of the International Astronomical Union at the beginning of the 21 st century have a marvelous opportunity to shed light on this old question of habitable worlds through observation, experimentation, and interpretation, without recourse to belief systems and without risking their lives (though some may experience rather bumpy career paths). The newly-named and funded, multi-disciplinary field of astrobiology is extremely broad in its scope and is encouraging IAU members to learn and speak the languages of previously disparate disciplines in an attempt to answer the big picture questions: 'Where did we come from?', 'Where are we going?', and 'Are we alone?' These are questions that the general public understand and support, and these are questions that are attracting students of all ages to science and engineering programs. These questions also push the limits of modern instrumentation to explore the cosmos remotely across space and time, as well as to examine samples of interplanetary space returned to the laboratory and samples of distant time teased out of our own Earth.Within my personal event horizon, the other planetary systems long-predicted by theorists have been uncovered, along with many whose structures were not predicted. The 'just-so' conditions requisite for the comfort of astronomers have been understood to be only a very narrow subset of the conditions that nurture extremophilic, microbial life. Thus the potentially habitable real estate beyond Earth has been greatly expanded and within the next few decades it may be possible to detect the biosignatures or technosignatures of inhabitants on distant worlds, should there be any.

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Section: Exploring the Cosmic Haystackmentioning

confidence: 99%

The evolution of life in the Universe: are we alone?

Tarter

2006

Proc. IAU

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“…The high gain of optical telescopes allows construction of beams that are much more collimated than those at longer wavelengths. Dispersion of the signal due to the interstellar medium (ISM) is negligible at optical wavelengths [4], and if measurements are made using photon counters operating at nanosecond timescales, there are very few sources of natural or man-made interference that can emit at sufficiently high intensity to confuse with an extraterrestrial signal [11]. Thanks to Moore's Law, instrumentation for optical SETI searches has become quite cheap relative to radio SETI, and is well-suited to piggyback operation on 1-metre class telescopes and above (see [20] for examples of both radio and optical SETI instrumentation).…”

Section: Introductionmentioning

confidence: 99%

Can Collimated Extraterrestrial Signals be Intercepted?

Forgan

2014

Preprint

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The Optical Search for Extraterrestrial Intelligence (OSETI) attempts to detect collimated, narrowband pulses of electromagnetic radiation. These pulses may either consist of signals intentionally directed at the Earth, or signals between two star systems with a vector that unintentionally intersects the Solar System, allowing Earth to intercept the communication. But should we expect to be able to intercept these unintentional signals? And what constraints can we place upon the frequency of intelligent civilisations if we do?We carry out Monte Carlo Realisation simulations of interstellar communications between civilisations in the Galactic Habitable Zone (GHZ) using collimated beams. We measure the frequency with which beams between two stars are intercepted by a third. The interception rate increases linearly with the fraction of communicating civilisations, and as the cube of the beam opening angle, which is somewhat stronger than theoretical expectations, which we argue is due to the geometry of the GHZ. We find that for an annular GHZ containing 10,000 civilisations, intersections are unlikely unless the beams are relatively uncollimated.These results indicate that optical SETI is more likely to find signals deliberately directed at the Earth than accidentally intercepting collimated communications. Equally, civilisations wishing to establish a network of communicating species may use weakly collimated beams to build up the network through interception, if they are willing to pay a cost penalty that is lower than that meted by fully isotropic beacons. Future SETI searches should consider the possibility that communicating civilisations will attempt to strike a balance between optimising costs and encouraging contact between civilisations, and look for weakly collimated pulses as well as narrow-beam pulses directed deliberately at the Earth.

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“…In a companion paper 8 we address the obvious next question, namely the backgrounds against which the putative pulsed optical beacon must compete.…”

Section: Backgroundsmentioning

confidence: 99%

<title>Targeted and all-sky search for nanosecond optical pulses at Harvard-Smithsonian</title>

Horowitz

Coldwell

Howard

et al. 2001

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

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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 1.5 m Cassegrain at the Harvard/Smithsonian Oak Ridge Observatory (Agassiz Station), with a coincidence triggering measurement of pulse width and intensity at subnanosecond resolution. A flexible web-enabled database, combined with mercifully low background coincidence rates (∼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 0.9 m 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 1.8 m 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 × 0 .• 2 patch of sky in transit mode, covering the Northern sky in ∼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.

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<title>Is there RFI in pulsed optical SETI?</title>

Cited by 8 publications

References 14 publications

The evolution of life in the Universe: are we alone?

The evolution of life in the Universe: are we alone?

Can Collimated Extraterrestrial Signals be Intercepted?

<title>Targeted and all-sky search for nanosecond optical pulses at Harvard-Smithsonian</title>

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