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TheMERGer-eventGamma-Ray(MERGR)Telescope
J.EricGrove,L.J.Mitchell,B.F.Phlips,C.C.Cheung,M.Kerr,R.S.Woolf(NRL)M.S.Briggs(UAH)J.S.Perkins(NASAGSFC)
MERGRisdesignedtodetectandlocalizeGamma-RayBursts(GRBs)–
particularlytheshortGRBelectromagneticcounterpartsofgravitationalwavedetectionsofneutron-starbinarymergers.Employingproventechnology,itcanbedeliveredonanaggressivescheduleforlaunchbytheDoDSpaceTestProgramin2021.
DevelopmentofMERGRatNRLissupportedbytheChiefofNavalResearch
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MERger-eventGamma-Ray(MERGR)Telescope
Motivationandplan•
WiththeannouncementofGW170817,theeraofgravitational
wavedetectionsofneutronstar(NS)binarymergershasbegun.
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MERGRwillworkasastandalonesystemoraspartofanetworkoftelescopes.Itwillincrease𝛾-rayskycoveragetodetecttheshortGRB(SGRB)counterpartsofNS-binarymergers.
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Tominimizecostandtimetofirstlight,MERGRisderiveddirectlyfromtheStrontiumIodideRadiationInstrumentationseries(SIRI-1andSIRI-2)demonstratorsdesignedandbuiltatNRLfortheDoDSpaceTestProgram.
TelescopeDesign•
MERGRconsistsof19DetectorAssemblies,eachwitha3.8
cmx1.27cmhexagonalSrI2:Eucrystalreadoutbyahexagonalarrayofsiliconphotomultipliers(SiPMs).
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SrI2:Euhashighdensity(4.2g/cm3),goodstoppingpower,andexcellentenergyresolution.
• Totalmass13kg,andtotalpower21W.
Right:CADrenderingofMERGRfromtheinstrument’szenithshowingthelocationsofthe19hexagonaldetectorsinaclosely-packeddomegeometry.
Left:Off-axisviewshowingMERGR’selectronicsbay.
Grove,MERGR|2
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MERger-eventGamma-Ray(MERGR)Telescope
Technology readiness•
MERGRinheritsdirectlyfromtwoinstruments,SIRI-1andSIRI-2,thatwedevelopedforDoDSpaceTestProgram(STP)launch.
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SIRI-1willspace-qualifystrontiumiodidescintillatorsandSiPMreadouts.IthasbeendeliveredtothespacecraftvendorandisscheduledforlaunchintoLEOonSTPSat-5.
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SIRI-2isafollow-ondetectorarrayofsevenSrI2:Eudetectorsforatmosphericburstmonitoring,scheduledtolaunchintoGEOinlate2018onboardSTPSat-6.
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Wehaveproposedtodesign,assemble,andtestMERGRtodeployby2021.TheDoDSTPprovidesalaunchopportunityandfundsforitsintegrationintothespacecraftbus,launchservices,andthefirstyearofexperimentdatacollection.
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UsingexistingalgorithmsdevelopedandtestedatNRL,instrumentflightsoftwarewillprovidereal-timeburstdetectionsandlocations,whichwillbetransmittedtotheGamma-rayCoordinatesNetworkforworldwidedistribution.
Grove,MERGR|3
SrI2:EudetectorsdevelopedforuseonSIRI-2.MERGRdetectorswouldbeidentical,expectforthickness.(Top)ExplodedCADrenderingofdetectorassembly.(Bottomleft)19-elementSiPM
arraydevelopedbyNRLforreadoutofhexagonalcrystals.(Bottomright)SIRI-2flightmodelhexagonalcrystalpriortoinstallationintodetectorhousing.
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MERger-eventGamma-Ray(MERGR)Telescope
Instrument performance• SensitivitytoE=20keV
to2MeV𝛾-rays,with4%spectralresolutionat662keV.Largefieldofview~6sr
(halfsky).
• HighdetectionefficiencyforGRBs:100%forfluence
>1.5ph/cm2withinFOV(belowleft).
• Localizations,68%radiiof6deg (and
