Package org.orekit.estimation.sequential

Class UnscentedKalmanEstimator

java.lang.Object

org.orekit.estimation.sequential.AbstractKalmanEstimator

org.orekit.estimation.sequential.UnscentedKalmanEstimator

All Implemented Interfaces:

ParameterEstimator

public class UnscentedKalmanEstimator
extends AbstractKalmanEstimator

Implementation of an Unscented Kalman filter to perform orbit determination.

The filter uses a PropagatorBuilder to initialize its reference trajectory.

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 etc...).
   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 total number of estimated parameters is m, the size of the state vector.

The Kalman filter implementation used is provided by the underlying mathematical library Hipparchus.

An UnscentedKalmanEstimator object is built using the build method of a UnscentedKalmanEstimatorBuilder. The builder is generalized to accept any PropagatorBuilder. Howerver, it is absolutely not recommended to use a DSSTPropagatorBuilder. A specific semi-analytical unscented Kalman Filter is implemented and shall be used.

Since:

11.3

Author:

Gaëtan Pierre, Bryan Cazabonne

Method Summary

Modifier and Type	Method	Description
Propagator[]	estimationStep(ObservedMeasurement<?> observedMeasurement)	Process a single measurement.
protected KalmanEstimation	getKalmanEstimation()	Get the provider for kalman filter estimations.
protected KalmanFilter<MeasurementDecorator>	getKalmanFilter()	Get the Hipparchus filter.
protected double[]	getScale()	Get the parameter scaling factors.
Propagator[]	processMeasurements(Iterable<ObservedMeasurement<?>> observedMeasurements)	Process several measurements.

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

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

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

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

estimationStep

public Propagator[] estimationStep(ObservedMeasurement<?> observedMeasurement)

Process a single measurement.

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

Parameters:

observedMeasurement - the measurement to process

Returns:

estimated propagator

processMeasurements

public Propagator[] processMeasurements(Iterable<ObservedMeasurement<?>> observedMeasurements)

Process several measurements.

Parameters:

observedMeasurements - the measurements to process in chronologically sorted order

Returns:

estimated propagator