Package org.orekit.estimation.sequential

Class SemiAnalyticalKalmanEstimator

java.lang.Object

org.orekit.estimation.sequential.AbstractKalmanEstimator

org.orekit.estimation.sequential.SemiAnalyticalKalmanEstimator

All Implemented Interfaces:

ParameterEstimator

public class SemiAnalyticalKalmanEstimator
extends AbstractKalmanEstimator

Implementation of an Extended Semi-analytical Kalman Filter (ESKF) to perform orbit determination.

The filter uses a DSSTPropagatorBuilder.

The estimated parameters are driven by ParameterDriver objects. They are of 3 different types:

1. Orbital parameters:The position and velocity of the spacecraft, or, more generally, its orbit.
   These parameters are retrieved from the reference trajectory propagator builder when the filter is initialized.
2. Propagation parameters: Some parameters modelling physical processes (SRP or drag coefficients).
   They are also retrieved from the propagator builder during the initialization phase.
3. Measurements parameters: Parameters related to measurements (station biases, positions etc...).
   They are passed down to the filter in its constructor.

The Kalman filter implementation used is provided by the underlying mathematical library Hipparchus. All the variables seen by Hipparchus (states, covariances, measurement matrices...) are normalized using a specific scale for each estimated parameters or standard deviation noise for each measurement components.

Since:

11.1

Author:

Julie Bayard, Bryan Cazabonne, Maxime Journot

See Also:

• "Folcik Z., Orbit Determination Using Modern Filters/Smoothers and Continuous Thrust Modeling, Master of Science Thesis, Department of Aeronautics and Astronautics, MIT, June, 2008."
• "Cazabonne B., Bayard J., Journot M., and Cefola P. J., A Semi-analytical Approach for Orbit Determination based on Extended Kalman Filter, AAS Paper 21-614, AAS/AIAA Astrodynamics Specialist Conference, Big Sky, August 2021."

Constructor Summary

Constructors

Constructor	Description
SemiAnalyticalKalmanEstimator(MatrixDecomposer decomposer, DSSTPropagatorBuilder propagatorBuilder, CovarianceMatrixProvider covarianceMatrixProvider, ParameterDriversList estimatedMeasurementParameters, CovarianceMatrixProvider measurementProcessNoiseMatrix)	Kalman filter estimator constructor (package private).

Method Summary

Modifier and Type	Method	Description
protected KalmanEstimation	getKalmanEstimation()	Get the provider for kalman filter estimations.
protected KalmanFilter<MeasurementDecorator>	getKalmanFilter()	Get the Hipparchus filter.
KalmanObserver	getObserver()	Get the observer.
protected double[]	getScale()	Get the parameter scaling factors.
DSSTPropagator	processMeasurements(List<ObservedMeasurement<?>> observedMeasurements)	Process a single measurement.
void	setObserver(KalmanObserver observer)	Set the observer.

Methods inherited from class org.orekit.estimation.sequential.AbstractKalmanEstimator

getBuilders, getCurrentDate, getCurrentMeasurementNumber, getEstimatedMeasurementsParameters, getMatrixDecomposer, getPhysicalEstimatedCovarianceMatrix, getPhysicalEstimatedState, getPropagatorBuilders, getReferenceDate

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.orekit.estimation.ParameterEstimator

getOrbitalParametersDrivers, getPropagationParametersDrivers

Constructor Details

SemiAnalyticalKalmanEstimator

public SemiAnalyticalKalmanEstimator(MatrixDecomposer decomposer,
 DSSTPropagatorBuilder propagatorBuilder,
 CovarianceMatrixProvider covarianceMatrixProvider,
 ParameterDriversList estimatedMeasurementParameters,
 CovarianceMatrixProvider measurementProcessNoiseMatrix)

Kalman filter estimator constructor (package private).

Parameters:

decomposer - decomposer to use for the correction phase

propagatorBuilder - propagator builder used to evaluate the orbit.

covarianceMatrixProvider - provider for process noise matrix

estimatedMeasurementParameters - measurement parameters to estimate

measurementProcessNoiseMatrix - provider for measurement process noise matrix

Method Details

getKalmanEstimation

protected KalmanEstimation getKalmanEstimation()

Get the provider for kalman filter estimations..

Specified by:

getKalmanEstimation in class AbstractKalmanEstimator

Returns:

the provider for Kalman filter estimations

getKalmanFilter

protected KalmanFilter<MeasurementDecorator> getKalmanFilter()

Get the Hipparchus filter..

Specified by:

getKalmanFilter in class AbstractKalmanEstimator

Returns:

the filter

getScale

protected double[] getScale()

Get the parameter scaling factors..

Specified by:

getScale in class AbstractKalmanEstimator

Returns:

the parameters scale

setObserver

public void setObserver(KalmanObserver observer)

Set the observer..

Overrides:

setObserver in class AbstractKalmanEstimator

Parameters:

observer - the observer

getObserver

public KalmanObserver getObserver()

Get the observer..

Overrides:

getObserver in class AbstractKalmanEstimator

Returns:

the observer

processMeasurements

public DSSTPropagator processMeasurements(List<ObservedMeasurement<?>> observedMeasurements)

Process a single measurement.

Update the filter with the new measurement by calling the estimate method.

Parameters:

observedMeasurements - the list of measurements to process

Returns:

estimated propagators