GPSSolut(2005)9:283–293DOI10.1007/s10291-005-0134-xORIGINALRalfSchmidMarkusRothacherDanielaThallerPeterSteigenbergerAbsolutephasecentercorrectionsofsatelliteandreceiverantennasImpactonglobalGPSsolutionsandestimationofazimuthalphasecentervariationsofthesatelliteantennaReceived:15November2004Accepted:2February2005Publishedonline:13April2005ÓSpringer-Verlag2005R.Schmid()InstitutfurAstronomischeundPhysikalischeGeodasie,TechnischeUniversitatMunchen,80290Munich,GermanyE-mail:schmid@bv.tum.deTel.:+49-89-28923193Fax:+49-89-28923178M.RothacherÆD.ThallerP.SteigenbergerForschungseinrichtungSatellitengeodasie,TechnischeUniversitatMunchen,80290Munich,GermanyE-mail:rothacher@bv.tum.deE-mail:daniela.thaller@bv.tum.deE-mail:steigenberger@bv.tum.deAbstractResultsoftheestimationofazimuth-dependentphasecentervariations(PCVs)ofGPSsatelliteantennasusingglobalGPSdataarepresented.Significantvariationsofupto±3–4mmthataredemon-stratedshowexcellentrepeatabilityovereightyears.TheapplicationoftheazimuthalPCVsbesidesthena-dir-dependentoneswillleadtoafurtherreductioninsystematican-tennaeects.Inaddition,thepaperfocusesonthebenefitofapossibletransitionfromrelativetoabsolutePCVs.ffApartfromsystematicchan-gesintheglobalstationcoordinates,onecanexpecttheGPSresultstobelessdependentontheelevationcut-oangle.This,togetherwiththeffsignificantreductionoftroposphericzenithdelaybiasesbetweenGPSandVLBI,standsforanimportantsteptowardmoreconsistencybetweendierentspacegeodetictechniques.KeywordsSatelliteantennaÆPhasecenfftervariationsÆTroposphericzenithdelayÆElevationcut-offIntroductionForseveralyears,absolutereceiverantennaphasecentervariations(PCVs)fromtwoindependentapproaches(calibrationinananechoicchamberandfieldcalibrationwitharobot)havebeenavailablethatareingoodagreementwitheachotheraswellaswiththerelativePCVspublishedbytheIGS(InternationalGPSService;seee.g.,Rothacher2001).Nevertheless,thelatterarestillused,althoughitiswellknownthatsystematicer-rorsaretheconsequence(e.g.,Schmidetal.2005).Theproblemofaterrestrialscalechangeofabout15ppbwithrespecttoITRF2000thatinitiallyprohibitedtheadoptionofabsolutePCVscouldbesolved,inthemeantime,bytheestimationofnadir-dependentsatelliteantennaPCVs(SchmidandRothacher2003).Thelatterarealsocalled‘‘absolute’’,namely,intermsofcom-patibilitytotheabsolutereceiverantennacorrectionsandnotinarealabsolutesense.Atthemoment,severalIGSanalysiscentersareworkingonthegenerationofbestpossiblesatelliteantennacorrectionvaluesinordertoprepareforatransitionfromrelativetoabsolutePCVswithintheIGS.GeandG.Gendt(2005)showedthatitisnotsu-cienttouseblock-ffispecificantennacorrectionvalues,astherearesignificantdierencesinthephasecenterbehaviorbetweencertffainsubgroupsofthesatelliteblocksorevenbetweenindividualsatellites(seealsoSchmidetal.2005).Thisholdsparticularlytrueforthephasecenterosets,butpossiblyforthePCVsaswell.FirstresultsofthereprocessingofffaglobalGPSnetworkperformedattheTechnicalUniversitiesofMunichand284Dresden(Steigenbergeretal.2004)pointedatthenecessitytouselongperiodsofdatafortheestimationofphasecenterosetsandvariationsofindividualsat-ffellites,asweekswithpoordeterminabilityalternatewithperiodsofhighaccuracyfortheestimatedparameters(highaccuracyforsmallanglesbetweentheorbitplaneandthedirectiontothesun).Sincetheselong-termre-sultsarenotyetfullyavailable,thepresentpaperwillnotconsi...