Gamma-Ray Burst Polarimeter (GAP) aboard the Small Solar Power Sail Demonstrator IKAROS

摘要

Thesmallsolar-powersaildemonstrator``IKAROS''isaJapaneseengineeringverificationspacecraftlaunchedbytheH-IIArocketon2010May21atJapanAerospaceExplorationAgency(JAXA)TanegashimaSpaceCenter.IKAROShasa20mdiametersail,whichismadeofathinpolyimidemembrane.Thesailconvertsthesolarradiation-pressureintothepropulsionforceofIKAROS,andacceleratesthespacecraft.TheGamma-RayBurstPolarimeter(GAP)aboardIKAROSisthefirstpolarimeterspecificallydesignedtomeasurethepolarizationofGamma-RayBursts(GRBs)fromspace,andwilldosointhecruisingphaseoftheIKAROSmission.GAPisamodestdetectorof3.8kginweightand17cminsizewithanenergyrangeofbetween50a€“300keV.TheGAPdetectorisnowamemberoftheinterplanetarynetwork(IPN)fordeterminingtheGRBdirection.Thedetectionprincipleofgamma-raypolarizationistheanisotropyoftheComptonscattering.CoincidencebetweenthecentralplasticComptonscatteringmediumanddiscreteCsIdetectorsdistributedaroundthesidesoftheplasticdefinestheCompton-scatteringangle,whichisexpectedtoshowanangulardependenceifpolarizationispresentinagivenGRB.Inthispaper,wepresenttheGAPdetectoranditsground-basedandonboardcalibrations.