Abstract: Usually，onorbitsatellitesarecontrolledbythegroundbasedTT&Cstations.Themoreon-orbitsatellitesareon-orbit，themoreTT&Cstationsandequipmentsareneededtobeconstructed.Meanwhile，duetotheEarthsurfacecurve，aTT&Cstationcancoveronlyafewpartofasatellite′sentireorbit.Highcoveragepercentageandmultipleaccesstechnologyenablethetrackinganddatarelaysatellitesystem（TDRSS）greatlyenhancingitspowerinspacedomainandfrequencytocontrolmuchmoreon-orbitlowearthorbitsatellites.Theanalysisonthelinkperformance，multipleserviceitems，multipleservicenumbersandcoveragepercentagemanifeststhataTDRSS，withitsSMAtechnology，cancontrolhugenumbersofon-orbitlowearthorbitsatellites.Threetrackinganddatarelaysatellites（TDRS）uniformlystationedatgeostationaryorbitcancontrolallChinacurrenton-orbitandtobelunchedsatelliteswithoutincreasingtheTT&Cstationsandequipments.ThenthreeSMAservicemodesweredescribed，whicheliminatetheTT&Ccontrolgapscausedbytheearthblackoutandquicklyresponsetoanyemergencyservice.WithTDRS′SMAsupport，asatellitecontrolcenterhasmorechoicetocontrolon-orbitsatelliteswhichimprovesitsmanagementefficiency，useefficiencyandmostimportantlytoimprovetheguaranteeofthesatellitesafety.

Key words: TDRS, SMA, lowearthorbitsatellite, on-orbitsatellitecontrol, forwardlink, returnlink