Weconsidertheproblemoftargetlocalizationbyanetworkofpassivesensors.Whenanunknowntargetemitsanacousticoraradiosignal,itspositioncanbelocalizedwithmultiplesensorsusingthetimedifferenceofarrival(TDOA)information.Inthispaper,weconsiderthemaximumlikelihoodformulationofthistargetlocaliza