Satellite Orbit and Ephemeris Determination using Inter Satellite Links

Software DescriptionInter Satellite Links5.2 Real time State EstimationThe real time state estimator requires linearised equations for the state dynamics and theobservations. Orbit propagation is a highly non linear process, as well as slant ranges are nonlinear observations. Thus, a non linear predictor is needed to derive approximate values forthe state and the predicted measurements. This task is performed by the orbit propagatordescribed above.No∆X Update > maxOrbit PropagatorFilter / Propagator ResetX Initial = X 0 + ∆X Update∆X = 0YesPredicted Satellite StateVector X 0Computation of linearizedTransition Matrix ΦTransition of Error StateVector ∆X PredictedComputation of linearizedMeasurement Matrix HCovariance PropagationCovariance Matrix PComputation of PredictedMeasurement z 0Predicted Residualr =∆x - H∆zKalman Gain Matrix KSatellite PlatformPropulsion ?YesAdditional NoiseAccounting for PropulsionUncertaintiesTransformation to ECI-J2000Coordinates (if necessary)Measurement ProcessorMeasurement zVarianceTarget IDSatellite Ephemeris/Station Co-ordinatesDatabaseMeasurement UpdateUpdated Error StateVectorUpdated CovarianceMatrixP U dOutput: Updated SatelliteStateX = X 0 + ∆X UpdatedFigure 5-2 State Estimation ProcessPage 74R. Wolf