Icarus223(2013)677–683 ContentslistsavailableatSciVerseScienceDirect Icarus journal homepage: www.elsevier.com/locate/icarus An initial meteoroid stream survey in the southern hemisphere using the Southern Argentina Agile Meteor Radar (SAAMER) D. Janchesa,⇑, J.L. Hormaecheab, C. Bruninic, W. Hockingd, D.C. Frittse aSpaceWeatherLab.,MailCode674,GSFC/NASA,Greenbelt,MD20771,UnitedStates bEstacionAstronomicaRioGrande,RioGrande,TierradelFuego,Argentina cDepartamentodeCienciasAstronomicasyGeofisicas,UniversidadNacionaldeLaPlata,LaPlata,Argentina dDepartmentofPhysicsandAstronomy,UniversityofWesternOntario,Canada eGatsInc.,Boulder,CO80302,UnitedStates a r t i c l e i n f o a b s t r a c t Articlehistory: Wepresentinthismanuscripta4yearsurveyofmeteorshowerradiantsutilizingtheSouthernArgentina Received20August2012 AgileMeteorRadar(SAAMER).SAAMER,whichoperatesatthesouthernmostregionofSouthAmerica,is Revised18December2012 a new generation SKiYMET system designed with significant differences from typical meteor radars Accepted24December2012 includinghightransmittedpowerandan8-antennatransmittingarrayenablinglargedetectedratesat Availableonline16January2013 lowzenithangles.WeappliedthestatisticalmethodologydevelopedbyJonesandJones(Jones,J.,Jones, W.[2006].Month.Not.R.Astron.Soc.367,1050–1056)tothedatacollectedeachdayandcompiledthe results into 1 composite representative year at 1(cid:2) resolution in Solar Longitude. We then search for enhancementsintheactivitywhichlastforatleast3daysandevolvetemporallyasisexpectedfrom ameteorshower.Usingthismethodology,wehaveidentifiedinourdata32showerradiants,twoof whichwerenotpartoftheIAUcommission22meteorshowerworkinglist.Recently,SAAMER’scapabil- itieswereenhancedbyaddingtworemotestationstoreceivemeteorforwardscattersignalsfrommeteor trails and thus enable the determination of meteoroid orbital parameters. SAAMER started recording orbitsinJanuary2012andfuturesurveyswillfocusonthesearchforunknownmeteorstreams,inpar- ticularinthesoutherneclipticsky. PublishedbyElsevierInc. 1.Introduction temaswellasextrasolarplanetaryenvironments(Malhotra,1995; Johansen et al., 2007; Walsh et al., 2011; Nesvorny´ et al., 2010; The collision of asteroids and disintegration of comets is the Wiegertetal.,2009). mainsourceofdustintheSolarSystem.Theseprocessesgiverise Meteor showers, in particular, are an excellent tool for these toathickcircumsolardiskofsmalldebrisknownastheZodiacal studies because they are the direct result of cometary mass loss DustCloud(ZDC).SeveralphysicaleffectsproducedbylargerSolar throughtheirapproachtotheinnerSolarSystem.Sporadicmete- System bodies result in the dust having relatively short lifetimes ors, on the other hand, are characterized by orbits which have maintaining somewhat a balance in their distribution preventing evolvedsignificantlyfromtheiroriginalatthemomentofejection thiscloudfrombecomingdustier.Forexample,theycanbeejected from their parent body and thus have lost their history.This im- fromtheSolarSystembyJupiter,thermallyobliteratedbytheSun, plies that, as oppose to showers, they cannot be associated with or physically fragmented by additional collisions amongst them. aparticularparentbodyand/orotherparticlesfromthesamepar- Also,aportionofthecloudissweptbytheplanets,andforthecase ent. Thus meteor showers are an excellent tool to constraint of those with atmospheres will produce the more familiar phe- dynamicalmodelsofcometaryevolution,bothorbitalandphysi- nomenaofionizationandlightproductionthatistermedmeteor. cal.Surveyingandstudyingmeteorshowerscanshedlighttocom- Wenowknowthatsimilarprocessesoccurinothersystemsascir- etarycompositionandstructure,dustejectionspeeds,parentbody cumstellardisksofdusthavebeenobserved,forexample,around masses and some times even constrain their period in the Solar Beta Pitcoris and Formalhaut. Thus understanding the nature of System (Sykes and Walker, 1992; Jenniskens, 2008; Wiegert and ZDCcanshedlighttothehistoryanddevelopmentoftheSolarSys- Brown,2004;Borovicˇkaetal.,2005).Brownetal.(2008)provides a detail account of known previous shower surveys, and as dis- cussedbytheauthors,meteorradarsareaneffectivetooltoper- ⇑ Correspondingauthor. form these surveys, in particular for smaller particles. It is also E-mail addresses: [email protected] (D. Janches), [email protected] (J.L. shown in that work that most of the known surveys were per- Hormaechea), [email protected] (C. Brunini), [email protected] (W. formed in the northern hemisphere with only (cid:2)10% taking place Hocking),[email protected](D.C.Fritts). 0019-1035/$-seefrontmatterPublishedbyElsevierInc. http://dx.doi.org/10.1016/j.icarus.2012.12.018 678 D.Janchesetal./Icarus223(2013)677–683 at southern latitudes, the latest of which involves observations Thermosphere (MLT) atmospheric region (Fritts et al., 2010b,a). performedduringa4yearperiodpriorto2000inwhichonlysix These enhancements were driven by two radical changes from streamswerefound(GalliganandBaggaley,2002a,b).Amorere- the typical systems: (1) significantly higher meteor counts (i.e. centsurveyutilizing2yearsofobservationswasreportedbyYoun- byatleastanorderofmagnitude)and(2)aneedforthemajority ger et al. (2009) in which over 30 showers were identified. The ofmeteordetectionstobeatsmallzenith(highelevation)angles. continual survey of meteor showers is important because it pro- BothneedswereaddressedwithSAAMER,whichwasdesignedfor videsinformationonthesometimescyclicannualstrengthinthe greatlyenhanced transmitterpeak power (60kW, rather than 6– activity of showers, and thus constrain models of dust evolution 20kWusedbymostmeteorradarsystems)andusesatransmitter intheSolarSystem.AgoodexampleistheLeonidsmeteorshower antenna(speciallydesignedbyMardocInc.)composedofeight(in- whichhaveproducedanumberofnoteworthystormsthroughout steadofone)3-elementcrossedyagis(ratherthan2-element)ar- history, particularly those in 1833, 1868 and most recently in ranged in a circle of diameter 27.6m (Fig. 1). SAAMER’s 1997–1998 period (Jenniskens, 2006) but currently its activity is operating frequency and bandwidth are 32.55 and 0.3MHz, veryweak. respectively. In the normal mode of operation, as it is the case Forthestudypresentedherewefocusontheutilizationofthe forthedatapresentedinthiswork,SAAMERtransmitsa2-kmlong SouthernArgentinaAgileMeteorRadar(SAAMER)andtheapplica- pulse with opposite phasing of every other yagi, directing the tionofthestatisticalmethoddevelopedbyJonesandJones(2006) majority of radar power into eight beams at 45(cid:2) azimuth incre- to estimate meteor shower radiants in single-station data collec- mentswithpeakpowerat(cid:2)35(cid:2)offzenith.Thisresultsinamajor- tion mode. We report a 4year survey of meteor shower radiants ityofmeteordetectionsatoff-zenithanglesbetween15(cid:2)and50(cid:2). utilizinganewgenerationSKiYMETsystemdesignedwithsignifi- Thereceivingarrayisformedbythetypicalfive-antennainterfer- cant differencesfrom typical meteor radars includinghightrans- ometerarrangement(Hockingetal.,1997;Jonesetal.,1998),allof mittedpowerandan8-antennatransmittingarrayenablinglarge whicharealso3-elementcrossedyagisenablingredundantmeteor detectedratesatlowzenithangles.Afulldescriptionofthenew position definition with errors less than 0.5(cid:2). Similarly as for the meteorradar system isprovidedin Section2whilea description Canadian Meteor Orbits Radar (CMOR; Brown et al., 2008), SAA- of our searching technique is provided in Section 3. The results MER uses the basic echo detection and analysis algorithms for arediscussedinSection4. theSKiYMETsystemsdevelopedbyHockingetal.(2001).Together, these upgrades increase the power at the small zenith angles of 2.SAAMER:systemdescription interestby(cid:2)23dBandthenear-zenith(i.e.elevationanglesgreat- erthan50(cid:2))meteorcountsby (cid:2)20integratedoverallazimuths. TheSouthernArgentinaAgileMeteorRadar(SAAMER)isaSKiY- This is shown in Fig. 2 where daily specular underdense meteor MET system deployed at the Estacion Astronomica Rio Grande traildetectedratesareshownforthenearly4yearlongperiodof (EARG) in the city of Rio Grande (53.8(cid:2)450800S; 67(cid:2)450500W), prov- observations utilized in this study. During the first 16months of ince of Tierra del Fuego, Argentina. The system, which has being operation,SAAMERtransmittedamonopulseatapulserepetition operationalcontinuouslysinceMay,2008was enhanced, relative frequency(PRF)of2140Hz,resultinginanexcessof10,000spec- tostandardmeteorradars,inordertoenableGravityWave(GW) ular trail detections daily (top panel in Fig. 2). In September of momentum flux measurements in the Mesosphere and Lower 2009, however, we changed the transmitting scheme to a 2-bit 0 dB -3 -6 -9 -12 -15 50 -18 -21 40 -24 30 -27 20 10 + North + + + ~90 m Receiving Array + + + o + Transmitting + + Array Electronics + + Hut + Fig.1. (left)AntennatransmitterandreceiverlayoutatRioGrande,TierradelFuego(withindividualantennasindicatedwithplussymbols);(topright)theanticipatedbeam patternpolardiagram.Theresultingbeamshavepeaksensitivityat35offzenithand(bottomright)SAAMERmeteordetectionsaboveouracceptabledetectionthreshold (total=12,317)for20May2008. D.Janchesetal./Icarus223(2013)677–683 679 30 0) 2008 0 0 1 5/13/2008 x 20 s ( or e et 10 M of # 0 0 100 200 300 Solar Longitude (degree) 0) 30 0 2009 10 9/2009 x 20 s ( or e et 10 M of # 0 0 100 200 300 Solar Longitude (degree) 00) 30 2010 0 1 s (x 20 or e Met 10 of # 0 0 100 200 300 Solar Longitude (degree) 0) 30 0 2011 0 1 x s ( 20 or e et M 10 of # 0 0 100 200 300 Solar Longitude (degree) 0) 30 0 2012 0 1/2012 1 s (x 20 or e et M 10 of # 0 0 100 200 300 Solar Longitude (degree) Fig.2. MeteorratesdetectedbySAAMERinthenormalmodeofoperationforthe(cid:2)4yearsofdatautilizedinthisstudy. codedpulseataPRFof1765Hzresultingina(cid:2)40%increaseinthe thatoftypicalsystemsispresentedinFrittsetal.(2012).InAugust dailycounts.Overall,thedetectedratesare(cid:2)2–3timeslargerthan 2010,weenhancedthecapabilitiesoftheradarbyaddingtwore- forexampleratesdetectedwithCMOR(Brownetal.,2008).Thisis motestationstoreceivemeteorforwardscattersignalsfromme- particularly remarkable considering that, most of the detections teor trails. The information provided by the outlying receiving occuroverhead,oppositetomostofmeteorradardesigns.Acom- stations enables the determination of meteoroid trajectories and parison between SAAMER’s meteor detection performance and speedsofmeteoroidsandthusleadstothedeterminationoftheir 680 D.Janchesetal./Icarus223(2013)677–683 orbitalparameters(Baggaleyetal.,1994;Brownetal.,2008).Orbi- locating these enhancements projected in equatorial coordinates talinformationhavebeenrecordedsinceJanuary2012andwillbe (i.e.RightAscentionRAandDeclinationd),meteorshowerradiants reportedinfutureworks. can be determined. For this purpose Jones and Morton (1977) developed a statistical technique, later improved by Jones and 3.Dataanalysis Jones (2006), which looks at each possible radiant and count the detections in a band perpendicular to each of them. This is per- TraditionalVHFmeteorradars(oftencalledall-skyradars)pri- formed by defining acceptance bands which are convolved with marilydetectthespecularreflectionofmeteortrailstravelingper- thefilterfunctiongivenby pendiculartothelineofsight ofthescatteringtrail.Thisimplies that their velocity vector (traveling direction) must fall within (1(cid:3)6(cid:2)h(cid:3)2þ5(cid:2)h(cid:3)4 forjhj6dh the plane perpendicular to the line between the radar and the xðhÞ¼ dh dh ð1Þ 0 forjhj>dh point in the sky where the echo was recorded (line-of-sight). As pointed out earlier, this information is accurately recorded using theinterferometerreceivingarray.Inotherwords,allpossibleme- where h is the angular separation to the center of the acceptance teorradiantswillfallwithinacircleperpendiculartothemeteor band.AssuggestedbyJonesandJones(2006)weimplementthisfil- line-of-sight.Iftherearemeteorsbelongingtoaparticularstream, ter using dh=4(cid:2) and searching all possible directions which lay thecirclesdefinedbytheseparticularmeteorswillallintersectin abovethelocalhorizonwitha(cid:2)1.8(cid:2)resolutioninbothequatorial onecommonpointproducinganenhancementabovethenoise.By coordinates. 90 60 30 XIC 225 270 315 0 45 90 135 180 ETA OCE -30 -60 -90 Fig.3. AsinglestationradiantactivitymapinequatorialcoordinatesdeterminedfromSAAMERdatafork=48(cid:2)inwhichactivityfromthreeshowersareevident.Thenearly 4yearofdataareincludedinthismap. 90 60 30 XIC 225 270 315 0 45 90 135 180 ETA OCE -30 -60 -90 Fig.4. 2DGaussianfittedresultstothedatashowninFig.3 D.Janchesetal./Icarus223(2013)677–683 681 ForthisworkandsimilarlytoBrownetal.(2008)wefocuson linkedradiantconstitutingashower.Thefinalsteponthesearch defining showers that are active year-to-year and thus we com- is to visually examine these linked radiants and those showing bined all data from all years into a single equivalent solar year, consistent positive drifts in RA, and consistent drifts throughout bybinningtheechodatabySolarLongitudeandconstructingradi- theiractivityperiodindweresingledoutforidentification.Fig.5 antmapsinequatorialcoordinates.Fig.3showsanexampleresult- shows the time evolutions of RA and d for OCE as well as a line ing from this methodology where enhancements due to the fitusedtocalculatethedrift. presence of three different showers at Solar Longitude (k) equal to48(cid:2)areevident.ThesearethegAquariids(ETA),DaytimenCet- ids(XIC)andSouthernDaytimexCetids(OCE).Notethatdueto 4.Resultsanddiscussions the high southern latitude location, SAAMER is prevented to see declinations much higher than (cid:2)35(cid:2), conjugate to CMOR which UtilizingthemethodologydescribedinSection3,weidentified efficiently detects meteors which radiant declination lies polar- over 60 radiant candidates. In order to unequivocally identify a ward(cid:2)(cid:3)35(cid:2). meteor stream, however, it is crucial to determine geocentric As a first step in the search and identification of radiant velocity and orbital information which are not accessible for the enhancements, we use the ETA and Southern June Aquiliids datapresentedinthissurvey.Duetothislimitation,weonlyfocus (SZC),twoofthestrongestannualshowers,intheseradiantmaps onreportingthoseradiantsforwhichidentificationwaspossible, todefinetheminimumrelativestrengthwithrespecttotheback- whichwascarriedoutinitiallybycomparingourresultswiththe ground noise that an enhancement needs to have in order to be Meteor Working List (MWL) reported by the International Astro- consider a potential candidate. This threshold is determined by nomical Union (IAU) Meteor Data Center (Jopek and Jenniskens, therelativestrengthoftheseshowersduringthefirstandlastdays 2011). For this, we search for values in k, RA and d reported in during which they are visible with respect to the sporadic back- the MWL, which represent those at maximum activity, that are ground. Each map for each degree of Solar Longitude was exam- withintheinitialandfinalvaluesderivedfromSAAMER’sobserva- ined by fitting a 2D Gaussian curve of (cid:2)4(cid:2)(cid:4)4(cid:2) on all tions.Asitwillbediscussedinthissection,duetoeitherinconsis- enhancements where the maximawas equal or greater than this tencieswiththeMWLorbecausetheparticularcandidatewasnot threshold.Fig.4showsthefittedresultsforthedatacorresponding presentinthelist,forafewparticularstreamswehavealsocom- toFig.3whereitcanbeobservedthatnotonlythethreeshowers pared our results with the surveys reported by Younger et al. weresuccessfullyidentified,butalsomostofthenoiseisremoved. (2009)and,whenpossibleduetotheirconjugatelocations,Brown AlistofpotentialradiantswascompiledforeachSolarLongitude. etal.(2010). Followingthisstep,wesearchintheresultinglistofpotentialrad- Table1presentstheradiantsforwhichidentificationwascon- iantsandselectthosewhichwerepresentforaminimumof3(cid:2)in firmed. The first two columns on this table provide the MWL Solar Longitude and within 2(cid:2) in RA and d between continuous showernameandIAUthreelettercode.Thefollowing6columns bins. We then recorded all these points together as a possible presenttheinitialandfinalobservedk,RAandd.Thesearedeter- mined from the first and last days during which the relative strengthoftheshowerisabovethenoisethreshold(seeSection3). 50 The last two columns in Table 1 present the measured temporal driftsobtainedbyfittingalinetotheobservedRAanddasafunc- tionofk(seeFig.5).Overallwehaveidentifiedthepresenceof32 40 showerradiantsintheobservationspresentedinthisstudy,similar es) tothenumberofshowersfoundinsouthernhemispheresurveyre- e 30 gr portedbyYoungeretal.(2009).Brownetal.(2008),usingCMOR de alsoinsinglestationmodeidentified45showers. A ( 20 FromtheresultsshowninTable1,itcanbeobservedthatfor R over60%oftheradiantsfound,theMWLvaluesfallwithintheob- servedinitialandfinalvaluesforatleasttwoofthethreecoordi- 10 nates, giving us confidence that SAAMER’s observations do indeed correspond to those showers. For three of the observed 0 showers (APS, CAP and SDA), the MWL values are very close to 30 35 40 45 50 55 60 thoseobservedonesbutsomedifferencesareevident.Forthecase Solar Longitude (degrees) of APS, the radiant was observed during 6(cid:2) in k, a much shorter 10 interval than the one observed by CMOR (Brown et al., 2010), and the final observed Solar Longitude is 13(cid:2) lower than the 8 MWLvalue.Similarlyforthecase ofSDAforwhichtheexpected maximumactivitySolarLongitudevalueis5(cid:2)lowerthantheinitial s) 6 valueobservedbySAAMER.TheAquariidcomplex,however,does e getquitecrowdedwithanumberofdifferentconstituentstreams e gr 4 aroundthesametimethatSDApeaks.Itmaybetheactiveradiants e d classifiedasSDAincludesothercomponents. δ ( 2 ForthecaseofMICandECR,althoughtheobservedSolarLongi- tudesaswellasRAagreewiththeMWLvalues,theobserveddec- 0 linations are 5–7(cid:2) higher than the expected values. In particular, theECRobserveddeclinationagreeswiththevaluesobservedby -2 Youngeretal.(2009)utilizingmeteorradarsinAustraliaandAnt- 30 35 40 45 50 55 60 arctica.Thisshowerislocatedataveryhighsouthernlatitudeand Solar Longitude (degrees) thusrecentdataarescarce.Wehopethatourfutureorbitaldeter- Fig.5. ActivityplotsfortheOCEmeteorshower. minationwillshedlightsastotheoriginofthesedifferences.Sim- ilarlywiththeSTA,althoughdifferencesbetweentheobservedand 682 D.Janchesetal./Icarus223(2013)677–683 Table1 ListofmeteorshowerradiantsobservedwithSAAMER. Name IAUCode ki kf RAi RAf di df DRA Dd DaytimeAprilPiscids APS 21 27 359 3.1 0.9 4.4 0.7 0.4 DaytimenCetids XIC 32 60 16.9 41.2 (cid:3)0.2 8.9 0.9 0.3 gAquarids ETA 35 59 329.6 346.5 (cid:3)4.5 3.6 0.7 0.3 SouthernDaytimexCetids OCE 40 57 16.5 32.1 (cid:3)9.1 (cid:3)1.9 0.9 0.4 aScorpiids ASC 58 61 249.7 250.2 (cid:3)28.4 (cid:3)29.8 (cid:3)0.1 (cid:3)0.2 SouthernlSagitariids SSG 67 94 255.2 278.5 (cid:3)30.2 (cid:3)33.9 0.9 (cid:3)0.1 DaytimeArietids ARI 71 85 39.52 48.36 21.6 25.8 0.63 0.3 SouthernJuneAquiliids SZC 74 113 304.4 327.7 (cid:3)37.4 (cid:3)28 0.6 0.3 NorthernJuneAquiliids NZC 85 95 297.9 303.3 (cid:3)9.2 (cid:3)6.6 0.6 0.3 SouthernrSagitariids SSS 84 100 286.6 298 (cid:3)28.4 (cid:3)23.5 0.6 0.3 aCapricornids CAP 96 113 305.3 318.8 (cid:3)7.1 (cid:3)2.5 0.9 0.2 JulyPhoenicids PHE 100 123 20.6 43 (cid:3)55.2 (cid:3)40.1 0.8 0.7 Microscopiids MIC 108 125 311.8 327 (cid:3)23.1 (cid:3)21 0.9 0.08 rCapricornids SCA 110 128 297.3 304.9 (cid:3)15.1 (cid:3)11.2 0.5 0.2 PiscisAustrinids PAU 114 127 332.8 350.7 (cid:3)21.4 (cid:3)24 1.5 (cid:3)0.4 99Aquariids NNA 124 134 353.8 357.2 (cid:3)26.9 (cid:3)21.4 0.5 0.5 AugustbPiscids BPI 126 167 325 359.9 (cid:3)10.8 1.9 0.9 0.3 SoutherndAquarids SDA 130 141 342.8 352.7 (cid:3)17.4 (cid:3)14.3 0.8 0.3 NortherndAquarids NDA 126 138 342.1 345.7 (cid:3)3.5 0.9 0.2 0.3 xPiscids OPC 162 172 0.4 5.9 1.5 3.6 0.5 0.2 SouthernTaurids STA 178 212 17.6 43 (cid:3)0.06 7.2 0.8 0.2 DaytimeSextantids DSX 179 194 148.8 159.4 0.07 (cid:3)6.2 0.7 (cid:3)0.5 Orionids ORI 205 212 92.2 97.7 15.1 16 0.8 0.03 NovemberxOrionids NOO 241 246 86.5 90.4 14.4 14.4 0.8 0.002 Geminids GEM 259 262 110.1 113.6 30.3 30.5 1.1 0.03 gCarinids ECR 280 291 159.4 169.3 (cid:3)51.5 (cid:3)53.3 0.9 (cid:3)0.2 fPuppids ZPU 234 240 124.6 127 (cid:3)45.4 (cid:3)43.9 0.3 0.09 cPuppids PUP 247 264 131.7 142.1 (cid:3)48.1 (cid:3)55.4 0.8 (cid:3)0.5 bPuppids PVE 274 276 139 140.6 (cid:3)49.5 (cid:3)51.2 JanuaryaPixids APY 299 301 129.9 133.2 (cid:3)33.7 (cid:3)37.1 1.6 (cid:3)1.7 DaytimenSagitariids XSA 288 293 281.3 285.7 (cid:3)19.5 (cid:3)19.5 0.7 0.04 DaytimeChiCapricornids DXC 291 300 299.8 302.8 (cid:3)33.9 (cid:3)32 0.4 0.2 expected declination exist, the observed ones agree well with ences from typical meteor radars including high transmitted thosereportedbyBrownetal.(2010).Thedisagreementbetween power and an 8-antenna transmitting array enabling large de- multipleindependentobservationsandthecataloguevaluesmay tectedratesatlowzenithangles.Weappliedthestatisticalmeth- reflectlimitationsoftheIAUMWL. odology developed by Jones and Jones (2006) to the data Therewerethreeobservedwelldefinedenhancementsthatoc- collectedeachdayandcompiledtheresultsinto1compositerep- curwithinthetemporalandspatialrangeofthePuppidscomplex. resentative year at 1(cid:2) resolution in Solar Longitude. We then Withoutorbitalorvelocityinformationthedefinitecorrelationof searched for enhancements in the activity which lasted for at whichenhancementcorrespondstowhichelementofthecomplex least three consecutive Solar Longitudes and showed consistent cannot be done. We nevertheless report them separately to positivedriftsinRAandconsistentdriftsthroughouttheiractivity emphasize the fact that were spatially and temporally resolved. period in d, which were then single out for identification. Using Inaddition,tworadiantsthatagreewiththosereportedbyYoun- thismethodology, wehaveidentifiedin our data 32showerrad- geretal.(2009)asAlphaPiscisAustralidsandSouthernPiscidsbut iants,twoofwhichwerenotpartoftheIAUcommission22me- arenotlistedintheMWLassuch.Thefirstradiantcorrespondsto teor shower working list. Preliminary analysis of SAAMER data the,previouslyunlisted,99Aquariids(NNA)shower(J.Jopek,Per- had suggested that, due to the rapid changes in SAAMER’strans- sonalCommunication,2012)whilethesecondonecorrespondsto mittedradiationpattern,which has nullsevery 45(cid:2), withrespect thelistedxPiscids(OPC)shower(seeTable7,p.726inJenniskens to all-sky meteor radar systems, meteor showers radiants would (2006),andshower217inIAUMWL).Thenamespresentedhere notbelocatedproperlyusingtheJonesandJones(2006)method- followtheofficialnomenclatureandshouldbereferassuchinfu- ology.Theresultingradiantcouldbeshiftedupto20(cid:2)fromtheir turereports(P.JenniskensandT.Jopek,PersonalCommunication, knownlocation(M.Campbell-BrownandW.Cook,PersonalCom- 2012). Finally, Younger et al. (2009) reported nine previously munication,2010).Inaddition,becauseittransmitshigherpower undocumentedshowers,noneofwhichwereevidentontheSAA- in a relatively smaller volume, SAAMER has the potential to be MER’sobservationsperformedforthisstudy.Wewillperformfur- more sensitive to lower mass meteoroids and in principle, less thersearchfortheseandothershowersintheorbitaldataenabled effective at detecting meteor showers, similar AMOR (Galligan bySAAMER’supgradesinthenearfuture. and Baggaley, 2002b; Brown et al., 2008). The results presented here show, not only that this is not the case, but also that SAA- MER is at least as effective as previous studies using traditional 5.Conclusions lower-power all-sky systems (Brown et al., 2008; Younger et al., 2009).ItisalsoimportanttonotefromTable1therangeofeclip- We presented in this manuscript an initial survey of meteor ticlatitudesthatSAAMERenablestosurvey.Itcaneffectivelyob- showerradiantsinthesouthernhemispherebyapplyingthesta- serve radiants from the ecliptic south pole to (cid:2)30(cid:2)N (e.g. tistical methodology developed by Jones and Jones (2006) to the Geminids), and thus once the orbital elements are accessible in data collected during the first 4years of SAAMER’s operation as future surveys will enable the detailed study of showers at high a single station radar. As described in Section 2, SAAMER is a southern latitudes (e.g July Phoenicids or Puppids complex), newgenerationSKiYMETsystemdesignedwithsignificantdiffer- which are unobservable from the CMOR’s location. D.Janchesetal./Icarus223(2013)677–683 683 Acknowledgments Hocking,W.K.,Fueller,B.,Vandepeer,B.,2001.Real-timedeterminationofmeteor- relatedparameters utilizingmoderndigital technology. J. Atmos.Solar Terr. Phys63,155–169. ThisworkwassupportedbyNSFAwardsAGS–0634650,AGS– Jenniskens, P., 2006. Meteor Showers and their Parent Comets. Cambridge 0944104andAST–0908118.WewishtothanktheEARGperson- UniversityPress. nelfortheirinvaluablehelpwiththeoperationofSAAMERandD. Jenniskens,P.,2008.TheParentBodiesofourMeteorShowers.LPIContributions. Johansen,A.,Oishi,J.S.,MacLow,M.-M.,Klahr,H.,Henning,T.,Youdin,A.,2007. Moser,P.BrownandM.Campbell-Brownforusefuldiscussions. Rapid planetesimal formation in turbulent circumstellar disks. Nature 448, 1022–1025.http://dx.doi.org/10.1038/nature06086. 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