anoveldecimeter-levelreal-timeorbitdeterminational g orithmusin gs p ace-bornegpsmeasurementswithse p arationandabsor p tionofbroadcaste p hemeriserror

thep ositionandvelocit yerror（ 3drms）ofthetraditionalreal-timeorbitdeterminational-g orithmusin gs p ace-bornegpsp seudo-ran g emeasurementsareu pto1.0mand1.0mm／ sg iventhelimitationsoftheorbitandclockerrorsofgpsbroadcaste p hemerisandthep seudo-ran g enoise.basedontheslow－var y in gcharacteristicofbroadcaste p hemeriserror,anovelmethodforhi g h-p recisionre-al-timeorbitdeterminationisp resentedinthisp a p erthatusesbothofthecarrierp haseandp seudo-ran g edataasmainobservationsandsetsthecorres p ondin gp arametersinthekalmanfiltermodeltose p arateandabsorbtheerrorsofgpsbroadcastorbitsandclockstoachievedecimeterlevelorbitre-sults.asimulativetestwascarriedouttop rocesss p ace-bornegpsdual fre q uenc ydatafor31consec-utiveda y sfromthechamp（ 320km），grace－a（ 460km） andsac－c（ 700km） satellitesatdiffer-entorbitalaltitudesusin gtheauto-develo p edsoftwaresatpods.thistestdemonstratesthatthep o-sitionandvelocit yerrors（ 3drms）oftheorbitresultsofthenew methodarereducedto30～40cmand0.3～0.5mm／ sres p ectivel y，meanin gthatorbitalaccuraciesareimp rovedb ymorethan50％ ascomp aredtothetraditionalmethod.