PoS(AASKA14)116 , 17 , 15 , Mike 10 http://pos.sissa.it/ , Alan Penny University Microwave 12 4 17 , Joseph Lazio Jet Propulsion 3 Cornell 15 8 , Jayanth 5 , Simon Garrington 9 , 7 Leiden University, NL; , , Zsolt Paragi 1 11 , 2 10 , Eric J. Korpela MPIfR, Germany; 7 14 , Jin Cheng-Jin 3 ) at 10 pc in less than 15 minutes, and with a 4 1 University of Leeds, UK; University of New South Wales; − 14 16 , Tim O’Brien , Heino Falcke 8 16 erg sec University of , Berkeley, USA; 3 17 ‡ . The flexibility of the signal detection systems used for SETI ) 10 1 , Melvin Hoare − ∼ 13 † , , UK; 12 , Dan Werthimer Oxford University, UK; 10 , James Benford 6 18 3 , erg sec 2 , , Ian Morrison 1 20 ∗ 3 , James Cordes 7 , 6 SETI Inst., USA 2 x 10 18 100 pc for emission comparable to that emitted by the Arecibo Planetary ∼ ∼ NIKHEF, NL; , Jill Tarter 9 NAOC, China; Radboud University, NL; 7 5 2 Delft University of Technology, NL , Leonid Gurvits 13 11 , 1 siemion at astron.nl modest four beam SETI observingbeam system could, out in to one minute, search every in the primary Speaker. EIRP = equivalent isotropic radiated power Both for Band 1 Radar (EIRP searches with the SKA willa allow much new wider algorithms variety to of be signal employed types that thanHere will previously provide we searched sensitivity for. discuss to the astrobiologicalhow and the astrophysical technical motivations for capabilities radiodetail of SETI several the conceivable and SKA SETI describe will experimentalcommensal, programs explore primary-user, on the targeted all radio and components survey SETI ofpossible programs parameter SKA1, with and SKA2. including space. project We the also discuss We enhancementsof target to commensal selection observing, them criteria how for the these varied programs, useadvantage and for cases in SETI. of the other case primary observers can be used to full The vast collecting area offlexible the digital Square electronics Kilometre and Array increased (SKA), computationaland harnessed exhaustive capacity, search by could for sensitive permit technologically-produced receivers, the radio most emissionintelligence from sensitive (SETI) advanced extraterrestrial ever performed.source roughly For analogous example, to terrestrial SKA1-MIDmissile high-power will warning radars (e.g. be radars, capable air EIRP route of surveillance detecting or a ballistic ∗ † ‡ Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. JIVE, NL; ASTRON, NL; c University, USA; Sciences, USA; 12 1 E-mail: Laura Spitler Laboratory, California Inst. of Technology, USA; of St. Andrews, UK;

Garrett David Messerschmitt Advancing Astrophysics with the Square KilometreJune Array 8-13, 2014 Giardini Naxos, Sicily, Italy Andrew P. V. Siemion Searching for Extraterrestrial Intelligence with the Chennamangalam PoS(AASKA14)116 could Andrew P. V. Siemion . Yet more compelling is the pos- does exist 2 Whether or not life occurs elsewhere in the is one of the most profound questions Although spectroscopy of extrasolar planet atmospheres or in-situ sampling missions in our has long played a prominent role in searches for extraterrestrial intelligence science can ask. As ofdespite this evidence that moment, the we necessary knowEarth-like abiotic of precursors planets only and (Petigura a environmental et single conditions example al.(Herbst are of 2013), & common. the van water Dishoeck emergence (Hogerheijde 2009) of have et life, biology now al. been and found 2011) underscoring in the and abundance, allure complex emboldening of the chemistry extraterrestrial field life. of astro- Knowing that Solar System may soon yieldparameters indirect of evidence life’s for evolution life thatselect beyond might means. Earth, lead the to deeper Thetechnology, intelligence question creation is the is of of only the addressable known technology, tracer only of andwhile intelligence by many detectable specifically much chemical over environmental interstellar tracers more distances. of modification However, basic2014), by life there exist can that types be of electromagnetic ambiguous emissions (Krasnopolskytechnology that et but could are al. plausibly not be 2004; known generated Rein to by ever et advanced ariseand al. naturally. conclusive As far indicators as we of know, these advancedcommunication emissions in technology, are particular definite and is presumably a superb itsis example intelligent in of fact creator. such the a most probe Radio detectable of distant extraterrestrial signature technology and of our own technology. (SETI), beginning with the first suggestions bysignals Cocconi near & 1420 Morrison (1959) MHz that might narrow-bandalong radio be these effective lines tracers by of Drake advanceda (1961), technology continuing variety through and of to early coherent more experiments radioTarter recent et signals investigations al. searching indicative (1980); for Horowitz of et technology al.(2001); at (1986); Gray Horowitz a & & wider Sagan Ellingsen (1993); rangemotivation Leigh (2002); of (1998); for Rampadarath Korpela frequencies, radio et et e.g. searches al. al. forliterature (2012); extraterrestrial (Oliver Siemion intelligence & et has Billingham al. been 1971;1. throughly (2010, Tarter discussed 2013). 2003), coherent in radio but the The the emissiontechnological development), salient is 2. arguments commonly electromagnetic are produced radiation the can byvelocity convey following: advanced currently information at technology known the to (judging maximum be bycertain possible, Earth’s types 3. of coherent radio radiosources, photons emissions 5. are are these emissions energetically easily can cheap distinguished transit vastplasma from to regions and astrophysical produce, of dust. interstellar background 4. space These relatively unaffected arguments bythe are gas, transmitting unaffected intelligence, by e.g. varying whether assumptions the aboutcan signal be the transmitted applied is motivation intentional roughly of or equally unintentional, to and a variety of potential signal types or modulation schemes. SETI with the SKA 1. Background 1.1 Signatures of Life exist, the race is on to discoversibility whether that or extraterrestrial not evolution it, may in have followed fact, aforth similar a track as life on form the possessing Earth,own. and intelligence brought and a technological capability perhaps far exceeding our PoS(AASKA14)116 15 GHz − 1 1.67 GHz). ∼ ≈ OH f Andrew P. V. Siemion 500 Hz. The vast majority of ∼ 3 1.42 GHz) and the hydroxyl radical (OH, ), the spectral region of relatively low natural noise between the ≈ 1 H f More recently, it has been suggested that various other types of signals possess merit as well. In addition to changing ideas about signal types, there has been steady growth in the number The first modern radio SETI experiments, including ’s pioneering work described In addition to the romantic allusion to terrestrial desert oases where life in a barren land gathers to galactic synchrotron background and emissionatmosphere, and absorption was by identified water early and asFaced oxygen in an with the ideal technological Earth’s limitations band that towindow, early made conduct SETI it radio experiments very developed SETI the difficult (Morrisonregion notion to et of of search the spectrum al. “water-hole,” the at 1977). an the entire especiallysitions bottom attractive of of neutral the hydrogen TMW (H, trough bound by the frequencies of hyperfine tran- Several authors have presented variations oncivilization the might appear idea to that be a a subtle plausiblesource’s variation signal inherent on from luminosity natural or emission, a to either very to attract advanced make thehand use attention 1994; of of Cordes a other & natural astronomers Sullivan 1995; (Cordes Sullivan 1993;ford & Lemarc- (2010); Cordes 1995; Benford Chennamangalam et et al. al.mitter 2015). (2010a,b) construction Ben- have and argued operation thatbe imply the preferred. terrestrial that Fridman economics broadband (2011) of rather concludeding beacon that than (FSK) trans- broadband narrow-band would emission systems be employing frequency-shift preferred might bearing key- by signals energy-conscious using civilizations seeking similar toMorrison capabilities (2012) transmit similarly to arrived information- at our the idea own.considering that robustness broadband to communication radio might Messerschmitt frequency be interference (2012); preferable (RFI), by andmay Messerschmitt further have deduced time-bandwidth & that extents this influenced emission by theother properties words, of the the coherence interstellar of medium abandwidth (ISM). modulated extent In information-bearing by signal the would combined be effectsinhomogenous of limited plasma the in occupying relative time motion the or of intervening theeffects space. source can and be Depending receiver corrected on and for, the the theydetect degree define information to either bearing limits which radio or these emission search sent parameters over of interstellar any distances. algorithm used to and diversity of suggestions of preferredcrowave frequencies window” (TMW, for Figure radio SETI. The so-called “terrestrial mi- radio SETI searches conducted since havefor continued this signals paradigm. of The this motivationsare for type searching readily are distinguishable numerous, from natural butcurrent sources, prominent technology. are among relatively them simple Were and anspecies, are are advanced that these easy civilization narrow-band properties to interested signals would detectcomponent in with be of intentionally many very of signaling valuable. our another terrestrialand radio Narrow-band continuous-wave communication sinusoids and (CW) are ranging radar, systems, alsosophisticated. e.g. but a carrier this prominent tones is changing as terrestrial technology becomes more in Drake (1961), focused on“narrow-band” identifying emission continuous is narrow-band defined emission.natural as In astrophysical electromagnetic the sources. emission SETI that context, astrophysical In is masers, the spectrally with radio narrower a regime, than spectral the width spectrally no narrowest narrower natural than sources are SETI with the SKA 1.2 Artificial Radio Emission PoS(AASKA14)116 2 = n 1.42 GHz) and 1000 ≈ H 300 MHz might f O 2 − H Andrew P. V. Siemion 2 O Transitions 100 2 O Atmospheric Rotational . Gindilis et al. (1993) identified e e , e O π 2 , H e , π 2 , 10 2 / (GHz) π 4 , Frequency π

Window Water 1 Terrestrial Microwave Microwave Terrestrial 1.67 GHz) the rest frequencies of H and OH hyperfine transitions by mathematically ≈ 1

Galactic Synchrotron OH

Background f 0.1 1

10

4.462336273 GHz as given in the reference 100 1000 (Kelvin) =

π The “terrestrial microwave window”: a relatively quiet between non-thermal galactic syn- Noise Temperature Noise H f e.g. Bands above and below the TMW present compelling opportunities as well. Loeb & Zal- 1 be worthwhile, including the factthese frequencies. that While some observations of that encroach themore on Earth’s difficult the most and upper detectable end less of emission sensitivefrequencies the due is are TMW less to tend leaked affected to increased at by become atmospheric theproduced interstellar noise, at and radio very interplanetary high transmissions plasma luminosities and at (Benford might 2010; these out be Benford that more et the al. easily received 2010b,a). signal Gindilis to (1973) noiseincreases pointed ratio by (SNR) more for than pulse an communication withGHz. order delay of Kardashev compensation magnitude (1979) between argued 1 that and advanced 10 civilizations GHz, transmitting reaching deliberate a beacons peak might around 56 darriaga (2007) have detailed a number of reasons why the band between 50 Figure 1: chrotron emission and molecularso-called rotational “Water transitions Hole” in bound by the the Earth’s frequencies atmosphere. of hyperfine Also transitions indicated of on neutral hydrogen the (H, figure is the the hydroxyl radical (OH, special “civilization signature constants,” e.g. SETI with the SKA sate, there was a convenientthat supply range already. of As large time telescopes progressed, other(1993) and “special lists sensitive frequencies” 55 were radio individual identified. “interstellar receivers communication Blair operating channel”25 & GHz in frequencies Zadnik based between on 500 scaling MHz and additional preferred frequencies based onexcited state. hyperfine transitions of neutral hydrogen in the PoS(AASKA14)116 Andrew P. V. Siemion 5 As our own radio technology advances, we will undoubtedly develop new ideas about what Since the inception of modern radio SETI, observers have grappled with a fundamental prob- Support for commensal observations will be critical for the SKA SETI program. For the dis- type of emission wethere might are expect certain from frequencies similarideal and technology terrestrial signal radio at SETI types work observatory that on wouldsignificant provide have another fractional near bandwidth, been world. continuous and particularly frequency flexible coverage Though to advocated over signal use to-date, a detection multiple search systems an algorithms. that Suchan could a open be system and programmed is extensible precisely digital whatreadily signal the program SKA processing flexible will backend, provide compute the - elements SKA through supplied with will their custom enable own hardware SETI algorithms, observers if and to perfectly necessary. optionally suited attach The user- to world’s conducting mostmost novel sensitive sensitive SETI radio search observations, for telescope artificial and will radio as emission thus ever we be conducted. detail below, will permit the 2. SETI Observations on the SKA 2.1 Commensality lem. The SETI searchand space sky is location, so that broad a in properdedication search many of requires dimensions, significant very amounts crucially large of including observing amountsto time both of a on telescope frequency single the time. science largest However, program, publicly-funded the let radio alone30 telescopes years one ago, as SETI speculative astronomers as devised SETI, a is1983). solution simply that By not they possible. taking dubbed “parasitic advantage More SETI” than of (Bowyerduplicated the et al. many fact that times the over amplified withcould sky very signal “piggy-back” little from on a added other radio noise users’gent telescope or observations can life loss be to without of conduct ever sensitivity, vastaccurate billing SETI sky name a astronomers surveys “commensal minute for observing,” signs of thisRadio of primary-user technique Emission intelli- time. is from enabling Nearby Now Developed theAstroPulse given Intelligent Search projects the Populations to for friendly use (SERENDIP), Extraterrestrial the SETI@home and Arecibo and hours more Observatory per to conduct year. SETI Astronomers observations for ofsal thousands all observing of stripes for a have wide now rangeof begun of observing to science time recognize programs without the that rigorous efficacy canobjects of constraints take or on commen- advantage fields. integration of period very Commensal or largeVLBA searches the amounts (Wayth et for need al. radio to 2011), target transients and specific or are other early commensal now operation transient routinely at and conducted the SETI JVLA, with pipelines GBT, the are LOFAR (Serylak in et development al. 2013),cussion Jodrell here, Bank we and define elsewhere. commensal observationslargely to independently, mean sharing two only or the more primary users field(s) using of the view observatory chosen by the primary observers. SETI with the SKA generally prefer frequencies higheridentified than several particular a “magic few frequencies” related GHz toperature the due and cosmic to hyperfine microwave background transitions less tem- in impairmentradio the astronomy from positronium technology the atom allows searches around ISM, over 200bandwidth, and many GHz. lessening hundreds of the Fortunately MHz extent modern to to GHz which of these instantaneous “magic frequencies” need be considered. PoS(AASKA14)116 SETI Andrew P. V. Siemion Commensal Control SETI Signal Processors Switch Ethernet 1 - n Beams 6 illustrates this scheme: a SETI observer employs an in- 2 Commensal META Information Observatory , most radio SETI experiments focus on narrow-band emission, and thus the appro- 1.2 Schematic Diagram of Commensal Observation on the SKA: a SETI observer employs an independent Signal detection in current SETI experiments is essentially an exercise in matched filtering, in priate matched filter is aaccount high for the resolution unknown Fourier relative transform, acceleration combined between with transmitter an and additional receiver. step A to suite of other which the filter template is definedin by Section the assumed characteristics of the transmitter. As discussed dependent beamforming capability to form phased-arrayof beams view within based the current on primary observatoryfor field(s) meta those beams information, to and SETI directs signalUsing the processors a that unprocessed technology perform digital such interference as voltage excision Ethernet,signal data and multiple processors signal copies detection. for of analysis a singlewith using beam the multiple can SKA techniques. be will directed be toare The conducted multiple additional in most this opportunities sensitive phased-array SETI for mode,products observations conducting but as parallel it well. is SETI worth analysis pointing on out imaging that there and2.2 raw Signal u-v Processing data From a SETI perspective, we envisioncan an be observing system independently in steered whichcessing multiple within hardware phased the where array SETI beams primary specific field-of-viewdesigned algorithms mode and are of implemented. fed operation is to The an excellent Allencan dedicated schematic function Telescope prototype signal Array’s (Welch for et pro- the al. way 2009). in which Figure such a system Figure 2: beamforming capability to form phased-arraymeta beams information, and within directs the the unprocessed current digital primary voltage field(s) data for of those view beams based to SETI on signal observatory processor via Ethernet SETI with the SKA PoS(AASKA14)116 (2.4) (2.1) (2.2) (2.3) , and from the is the apparent 1 − Andrew P. V. Siemion apparent f 02 Hz s . 0 5 / 3 5 ∼ ± the intrinsic bandwidth of the / 9 i SM − b  ∆  b t

⊥ ∆ R R V the integration time. Here we assume 100 t r   5 5 the speed of light. Because we are search- / sys / 6 6 c S − GHz c − rest GHz f ν ν , of a narrow band signal in one polarization is i thresh F V −→ 7 dt σ d = = i 300 Hz 097 Hz ˙ b f . ∆ 0 = i S = IPM = is the system equivalent flux density (SEFD) of the receiv- − i ISM F . − sys 1 in terms of flux rather than flux density to more intuitively relate S − i broad F ν broad ∆ ν ∆ 1 Hz s . 0 ∼ − is the SNR, is the spectral channel bandwidth and 2 b is the intrinsic flux density of the transmitter, ∆ thresh i σ S is the line of sight relative velocity between receiver and source, , and have expressed b V −→ ∆ The maximum rotational contribution is negative because it occurs for a source observed from the equator at zenith. For narrowband signals, the “Doppler drift,” or changing apparent frequency due to the relative Narrow band signals are spectrally broadened by both the ISM and interplanetary medium Where Here we will use the case of narrow-band detection as an illustrative example of SETI signal The minimum incoherently detectable flux, < 2 i b ing telescope, acceleration between the transmitter and receiver is given simply by: transmitter, ∆ experimental sensitivity to terrestrial transmittertotal power apparent levels, luminosity which (or are EIRP). commonly described by where frequency of the transmitter for constant velocity and (IPM), with a magnitude equal to (Cordes & Lazio 1991; Siemion et al. 2013): ing for emission at ansome unknown unknown constant frequency, relative the velocity overall ismaximum Doppler unimportant contribution shift from for the imposed detection. Earth’s on As orbitalEarth’s a points motion rotation of signal at is reference, 1 due GHz the to is and processing and for calculating the sensitivity of SKAsources SETI of observations. a Although given the luminosity sensitivity would to varythe somewhat sensitivity for algorithms expressions detecting and other types calculationsweakly-coherent of used detection signals, schemes here (Sullivan are & roughly Mighell 1984; correct Gulkis for 1984). other incoherent or SETI with the SKA algorithms might be effectively employedanalysis in (Biraud a 1983; Maccone SETI 1991), experiment,autocorrelation autocorrelation including (SWAC) (Morrison (Gardner principal 2012) & and component Spooner automatic 1992),& modulation Nandi symbol-wise classification 2010) (AMC) and (Aslam references therein,putational cost. but are SETI not experiments yet on intional the performance widespread SKA thanks use will to largely benefit the due continuing from to Moore’s1965), significant law their and increases growth com- in in thus the computa- will electronics be industryflexible (Moore able signal detection to systems. consider Moreover, implementing for the someparallel” most and of part can these these readily techniques techniques be are using scaled “embarrassingly the to accommodate SKA’s enhanced capabilities. given by: PoS(AASKA14)116 is the ⊥ V Andrew P. V. Siemion out to several kpc, the

R 100 ∼ > 4 in the minimal case), is required. R − is the Solar impact distance, 5 / R 6 − GHz ν 8 0.1 Hz ∼ 3 25M targets, and could be readily constructed from the expected ∼ is the observing frequency in GHz, (Perryman et al. 2001) following a prescription similar to that used in the “HabCat” GHz ν GAIA Field (Siemion et al. 2013) or the Galactic Center region (Shostak & Tarter 1985). The = 25 km/sec, SM from Cordes & Lazio (2002) ⊥ In practice, the vast majority of SETI observing on the SKA will be conducted commensally The combined influence of the above effects thus dictate the parameters of an optimal search Generally speaking there are two possible SETI observing strategies, targeted observations of However, a HabCat-like catalog should be supplemented using additional strategies. For ex- Where V 3 ). This fact, combined with many other unknowns, will lead to a wide range of views regarding 2.4 how SETI observations should be conducted onthese the proposals SKA. should As is be the subjectbe case to with observed any peer with science highest review program, and priority.approaches those Tarter to (2001) targets SETI and deemed target references selection most in therein compelling detail. detail will the varied proposed with other science programs, employing a signaling processing searches system using that will multiple be phased-array capable beams ofall-sky over conduct- catalog only providing a a fraction number of of theat primary targets least beam. per equal primary Thus to field an the of view, number at of the phased-array highest SETI frequencies, beams (2 transverse (perpendicular to the line of sight)dependent velocity scattering of the measure, source a in km/sec measureintegrated and along of SM the the the line direction of electron sight. densitytotal For spectral fluctuations most broadening lines (c.f. is of no sight Rickett more with than 1990) relative merit of theseradio two transmitters, approaches which depends at strongly presentcan is on be largely the drawn unconstrained luminosity (Tarter from 2004), function examining although of the some luminosity artificial insight distribution of terrestrial transmitters (See Section Such a catalog would consist of for narrow-band transmitters. Around 1and GHz (unknown) for drift example, correction frequencyrial up resolutions transmitters of to on order a a 0.1 few planet Hz distances Hz/sec up of to around would 1 five permit kpc. times Algorithms optimum largereterized, used detection and to in detect rotating of that other five types equato- they times of will signalsbased faster will search on than be the or the similarly expected param- average Earth properties over at of similar the signal parameters and and communication will channel. 2.3 also be Target Selection constrained individual objects or fields thoughtof to large be swaths especially likely ofKepler to the host sky. intelligent life Occasionally or hybrid blind approaches surveys are employed, e.g. surveys of the ample, a simple isotropic volume-selectediment sample for of a number is of anthat reasons. ideal can Most lead target importantly, us set it to for ameliorates concentrateA a the SETI search SETI inherent efforts of exper- anthropocentric on a bias environments blind similar volume-limited to sample our of own stars planetary is system. premised only on the notion that intelligent results of catalogue of habitable stars (Turnbull & Tarteroplanet 2003a,b). systems That that is, appear essentially choosing most starsour conducive and own to ex- Solar life system. as we know it, or in other words are similar to SETI with the SKA PoS(AASKA14)116 Andrew P. V. Siemion depicts one possible realization 4 of latitude is especially attractive. ◦ 9 of longitude and 30 ◦ ). Extrapolating from humanity’s exploration of space, it is likely 3 An illustration of a 2-planet conjunction in an extrasolar planetary system along a line of sight to the Earth. Another idea that may inform the construction of an SKA SETI catalog is the notion that The plethora of multi-planet systems now known present a unique opportunity for Other additions to aas SKA signposts SETI or target natural listtransmitted amplifiers, might at e.g. include a specific natural maser using sources transition a frequency that (Cordes maser could 1993; filament Cordes serve & to either Sullivan amplify 1995). a narrow-band signal of such a GHZ(arbitrary from units) Morrison is & proportional to Gowanlock theall (2014). habitable accumulated planets time within For available that for pixel each out intelligenceepochs. pixel to to a The shown, evolve maximum available times range across the for of plotted intelligence 5 to kpcsupernova metric putatively from events. emerge Earth, occur summed during As over gaps all shown, between this nearby centre work and suggests spanning that approximately a region 60 of the sky centered on the galactic Figure 3: perhaps there are preferred regions“galactic of habitable zones” the (GHZ), e.g. forrate and the based proximity development of on supernovae of stellar (Lineweaver et complex population al. 2004). life, similarity Figure so-called to the Sun or a low that a more advanced civilizationmultiple having planets similar in proclivities would their explore starcommunication, and system. radar perhaps imaging colonize These or explorations radarwhich could we mapping very use of easily the orbital Arecibo include debris,these Planetary planet-planet perhaps systems Radar similar to during image to alignments objects the wouldpublished in way allow ephemerides our in us own of Solar to these System. potentiallyand known many eavesdrop Observing systems more on readily such this systems enable are emission. calculation expected to of The be conjunction discovered in times, the coming decades. performing SETI searches at particularly advantageousof sight times to - the epochs Earth of (See conjunction Figure along a line SETI with the SKA life requires a stellar hostthat in is order exceedingly to well develop. studiedtributes of at It the many also sample wavelengths. probes willof a In allow technologically-produced us diverse the radio nearby to event emission. place stellar of It strong population alsoimportant a and allows if non us the broadly detection, to artificial applicable search radio these limits very transmitter at- technologically on deeply, luminosity produced which the function radio may presence declines luminosity. be steeply much past our own PoS(AASKA14)116

1000 100 10000 Propensity Metric Propensity Andrew P. V. Siemion 180 150 120 lists several terrestrial transmitters 90 5 , a transmitter is detectable if its EIRP is 60 6 30 10 0 ergs/sec (airport radar) is detectable only with SKA2. -30 17 Galactic Longitude (deg) -60 -90 ergs/sec (planetary radar) is detectable with all of the telescopes shown, while -120 20 -150 depicts the sensitivity of each component of the SKA to narrow-band transmitters 6 Contour map plot of the relative propensity for the emergence of intelligence as a function of telescope point-

-180 0

60 30 90 -60 -90 -30 Galactic Latitude (deg) Latitude Galactic Figure Absent of the actual detection of an artificial extraterrestrial radio transmitter, our best points of at 15 pc, as compared withSearch parameter other assumptions facilities here actively match performing roughly SETI whatof might searches be commensal over expected observations, the for namely a same significant band. a fraction appropriate maximum signal integration detection time systems of the 10 rawmost minutes. sensitivity sensitive of SETI As the shown, system SKA with can in be the leveraged world. to create the In Figure that produce emission in thedescribed bands by probed their by equivalent thesuch isotropically SKA, transmitters radiated along on power with the (EIRP). theirare Earth pseudo-luminosities The included as is simply approximate to also number describebe listed. of the sensitive energetics to These of in terrestrial transmitters anprecisely that analogs intuitive alike SKA way. of that SETI artificial Although experiments searched inoutput transmitters might for power many in in cases such radio these a SETI transmitters waytransmissions that produce as experiments, they a emission in would simple not sinusoid. other be cases as detectable they as modulate is implied their by considering their above the curve for a givenan telescope. EIRP Thus of in 2 the x observing 10 scenario presented, a transmitter with Figure 4: ing direction in galactic coordinates,where based each on supernova pixel event represents rates. approximatelyunits) An one is equal-area square sinusoidal proportional degree projection to on isthat the the employed, pixel sky. accumulated out For time to each available ato pixel, maximum for emerge the range intelligence occur plotted of to metric during 5 evolve (arbitrary kpc gapsincluded across from between in all Earth, the nearby summed habitable summations. supernova over planets events.time all For for within epochs. this Only land-based plot, complex gap The life a times available toto times threshold exceeding evolve) intelligence). for plus of a 0.6 intelligence 2.15 minimum Gyr Gyr threshold (the is assumed are minimum employed, time consisting for of complex 1.55 life2.4 to Gyr further (the Sensitivity evolve assumed reference for the sensitivity ofdetect, radio SETI come experiments, from and our the luminosities own of terrestrial sources technology. we might Figure a transmitter with an EIRP of 1 x 10 SETI with the SKA PoS(AASKA14)116 Few Dozens Hundreds Andrew P. V. Siemion Number on Earth Number 12 17 20 ~1 x 10 ~5 x 10 (ergs/sec) ~2 x 10 11 , that only SKA2 has the ability to detect TV and Luminosity (EIRP) Luminosity 7 Radio Long Range Aircraft Long Range Radar and TV High Power Interplanetary Radar depicts what sensitivities could be attained in a more optimistic scenario, in which Transmitter Type Transmitter 7 A table of terrestrial analogs of artificial extraterrestrial radio sources, including the pseudo-luminosity, SETI searches with the SKA1 facilities will build from an active base of theoretical and ex- Figure As is the case with many large scientific facilities, we expect the full capabilities of the SKA perimental work being done in the field with existing large-scale facilities, but the combination radio station-like transmitters. With thebe expected sensitive number to of these planetary in the systems singlehuman-like for digits, civilization which any invisible. it reduction would in sensitivity of SKA2 could render a nearby 3. Summary SETI was the primary observing purposescience or commensal case observations very were well performed matched withthe another to minimum SETI. channelization bandwidth Here permitted we by ISM assumeradio and an IPM transmitter integration effects. luminosities time As shown, of similar withthousands 60 SKA1, to of minutes, our stars and high acrosswill the power be entire radars detectable terrestrial will from microwave be hundreds window,time detectable of and have the thousands with from sensitivity to of SKA2 tens detect stars. these radio of from emission signals a Further, similar few with in of power SKA2 our to nearest we our neighbors. own will TV for and radio the stations first to emerge over time.breadth of SETI unexplored is parameter very spaceraw in well sensitivity. SETI suited is Although to quite increased large conductingof sensitivity in early and additional terms phased-array digital deployment of beams, capabilities, science, frequency will especially coverage50% as increase and the build-out the the availability of depth SKA1 and acrossin breadth the a of board luminosity-limited SETI a survey. More on SETI distant the program targetsit SKA, could could is be begin with reserved worth to for pointing probe full the sensitivity. out, However, nearer as targets shown in Figure as expressed by the equivalentpresent on isotropically Earth. radiated power (EIRP) and the approximate number of such transmitters Figure 5: SETI with the SKA PoS(AASKA14)116

2 15, 10 to a = − σ 3 GHz to a lu- SKA2 LOFAR Arecibo GBT ATA SKA1 (LOW/MID) SKA1 (SUR) − Andrew P. V. Siemion 1 10 more than ten thousand stars − ergs/sec (planetary radar) is detectable with all of the ergs/sec, over a larger band. Conservatively, ergs/sec (airport radar) is detectable only with SKA2. 0 20 18 17 10 10 12 ∼ Frequency (GHz) 10 minutes. A transmitter is detectable if its EIRP is above the curve = t −1 10 ergs/sec Backus (1998). In a five year commensal campaign, SKA1 19 2 x 10 ∼ 5 Hz and integration time . 0 = b Sensitivity of each component of the SKA to narrow-band transmitters at 15 pc, as compared with other ∆ −2

10 15 18 17 16 20 19

Historically, performing SETI experiments effectively with large telescopes has been tech- 10 10 10 10 10 10 Minimum Detectable EIRP (erg s (erg EIRP Detectable Minimum )

1 − for a given telescope. Thus atelescopes transmitter shown, with while an a EIRP of transmitter 2 with x an 10 EIRP of 1 x 10 of raw sensitivity, flexible electronics andmagnitude increased improvement computational in capacity the will speed, enable depththorough orders-of- and targeted breadth SETI of search previous previously SETI conducted experiments. surveyed The 1000 most stars over 1 bandwidth Sensitivities for the Greenguides. Bank Telescope For (GBT), LOFAR we Arecibo assumevan and Leeuwen only LOFAR et core were al. stations (2009). taken are from used. those Allen facilities’ Telescope observing Array (ATA) sensitivity was taken from minosity limit of Figure 6: facilities actively performing SETI searches over the same band. Here we assume a significance threshold could survey every star in its declination range within 60 pc nically and politically difficult.which SKA SETI will observations are be a theobserving conscious first mode. part world-class of Our telescope the most design ever powerfulavailable process constructed tool and and for to accessible are to search available astronomers for as around otherfield a the intelligent of facility world, life SETI infusing in new and the peopleespecially maximizing cosmos and searches will the ideas be for in scientific intelligent to return the life,public, of and have this the a component SKA. remarkable of Searches the abilitypublic SKA for to engagement. science life spark case From will beyond the a offer imagination Earth, of purely ample of scientific opportunity life for the standpoint, on outreach the another and discovery worldwould of would suggest an provide that independent strong evolution genesis evidence proceedstransmission that to towards be life this received is and end decoded, common, wecontained easily. and can therein, only its but Were conjecture surely intelligence an what our thoughts information-containing human and culture ideas would might be be enriched in unimaginable ways. SETI with the SKA luminosity limit an order of magnitudein fainter, ten years SKA2 could surveyterrestrial every aircraft star radars within over the 60 entire pc terrestrial to microwave a window. luminosity limit equal to the EIRP of PoS(AASKA14)116 12 = Band 5 σ Band 4 SKA1 (SUR) SKA1 (LOW/MID) SKA2 Band 3 Andrew P. V. Siemion Band 2 , significance threshold 3 − Band 1 than discussed in Section 2.2, reflect the b ∆ = 0.1 pc ∗ n 1 0 10 10

13 Band 5 Band 4 Band 3 Band 2 Part of this research was carried out at the Jet Propulsion Laboratory, Cali- Band 1 60 minutes. For luminosities similar to our terrestrial aircraft radars we assume bandwidth = t LOW The number of stars in the solar neighborhood from which narrow-band emission would be detectable ). The search parameters shown here, namely the smaller value of 1

01 Hz and for luminosities similar to terrestrial TV/radio-like signals (right) we assume fully coherent integration − 2 1 0 6 5 4 3 . t

0

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