Abstract: Thetimeinformationevaluatedfromthemessageoftheautomaticidentifyingsystem（AIS）isofmostimportanceinmonitoringandcontrollingoftheglobalvessels.Aimingatcontinuouslymonitoringsomeparticularvessels，thetimeinformationintheAISmessagesoftheAISsystemsonboardboththeTianTuo-1（TT1）andTianTuo-3（TT3）micro-nano-satelliteswasstudied.Firstly，astatisticalanalysiswasperformedbyemployingtheAISdatareceivedbytheTianTuo-1nano-satelliteduringitsonorbitoperation.TheresultssuggestthatitisimpossibletoobtainthetimeinformationmerelybytheAISmessageitself.Secondly，thecompositionandformatoftheAISmessagereceivedbytheTT3-AISwasstudied.IntheTT3-AISsystem，atimeflagwasgeneratedeveryminutetobeinsertedintothereceivedAISdatapackage.ThustheTT3-AIShasagoodfunctiononaddingthetimeinformationtotheAISmessages，whichwillbehelpfulformonitoringandcontrollingoftheglobalvessels.

Key words: TianTuo-1nano-satellite, TianTuo-3micro-nano-satellite, space-basedAIS, SOTDMA, time-flag