Abstract: AlowEarthorbit(LEO)satellitecanbestabilized    in3-axisbycorporatelyusingamagnetometer,reactionwheelsand3-axismagnetorquerrods.Itischallengingtodeterminate anappropriateattitudeforLEO.Toaddressthischallenge,thealgorithmsofextendedKalmanfilter(EKF)andunscentedKalmanfilter(UKF)werecomparedandasolutionwasproposedbyexploringtheinfluenceofthegeomagneticmodelerror,themagneticmeasurementerrorandtheremanenceontheperformanceofattitudedetermination.Inaddition,thecalculationofmeanandcovariancequaternionwasderived.TheEKFandUKFwereintroducedtoattitudedetermination,andthefactorswhichhaveinfluenceonthealgorithmperformancewerediscussed.Twoalgorithmswerecomparedonestimationaccuracy,convergencetimeandcomputationcomplexity.Withtheaccuracyrequirementsandthehardwarelimitations,theEKFalgorithmwasfinallychosenfortheattitudedetermination.Simulationresultsshowthattheearthpointingaccuracyoftheproposedsolutioncanreach1°withthestabilityof0.1(°)/s.

Key words: Kalmanfilter, UnscentedKalmanfilter, Geomagneticmeasurement, Attitudedetermination, LowEarthorbitsatellite