Package org.orekit.estimation.sequential

Class KalmanEstimator

java.lang.Object

org.orekit.estimation.sequential.KalmanEstimator

public class KalmanEstimator
extends Object

Implementation of a Kalman filter to perform orbit determination.

The filter uses a NumericalPropagatorBuilder to initialize its reference trajectory NumericalPropagator.

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. 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.

A KalmanEstimator object is built using the build method of a KalmanEstimatorBuilder.

Since:

9.2

Author:

Romain Gerbaud, Maxime Journot, Luc Maisonobe

Method Summary

Modifier and Type	Method	Description
NumericalPropagator[]	estimationStep(ObservedMeasurement<?> observedMeasurement)	Process a single measurement.
AbsoluteDate	getCurrentDate()	Get the current date.
int	getCurrentMeasurementNumber()	Get the current measurement number.
ParameterDriversList	getEstimatedMeasurementsParameters()	Get the list of estimated measurements parameters.
ParameterDriversList	getOrbitalParametersDrivers(boolean estimatedOnly)	Get the orbital parameters supported by this estimator.
RealMatrix	getPhysicalEstimatedCovarianceMatrix()	Get the "physical" estimated covariance matrix (i.e.
RealVector	getPhysicalEstimatedState()	Get the "physical" estimated state (i.e.
ParameterDriversList	getPropagationParametersDrivers(boolean estimatedOnly)	Get the propagator parameters supported by this estimator.
NumericalPropagator[]	processMeasurements(Iterable<ObservedMeasurement<?>> observedMeasurements)	Process several measurements.
void	setObserver(KalmanObserver observer)	Set the observer.

Methods inherited from class java.lang.Object

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

Method Detail

setObserver

public void setObserver(KalmanObserver observer)

Set the observer.

Parameters:

observer - the observer

getCurrentMeasurementNumber

public int getCurrentMeasurementNumber()

Get the current measurement number.

Returns:

current measurement number

getCurrentDate

public AbsoluteDate getCurrentDate()

Get the current date.

Returns:

current date

getPhysicalEstimatedState

public RealVector getPhysicalEstimatedState()

Get the "physical" estimated state (i.e. not normalized)

Returns:

the "physical" estimated state

getPhysicalEstimatedCovarianceMatrix

public RealMatrix getPhysicalEstimatedCovarianceMatrix()

Get the "physical" estimated covariance matrix (i.e. not normalized)

Returns:

the "physical" estimated covariance matrix

getOrbitalParametersDrivers

public ParameterDriversList getOrbitalParametersDrivers(boolean estimatedOnly)
                                                 throws OrekitException

Get the orbital parameters supported by this estimator.

If there are more than one propagator builder, then the names of the drivers have an index marker in square brackets appended to them in order to distinguish the various orbits. So for example with one builder generating Keplerian orbits the names would be simply "a", "e", "i"... but if there are several builders the names would be "a[0]", "e[0]", "i[0]"..."a[1]", "e[1]", "i[1]"...

Parameters:

estimatedOnly - if true, only estimated parameters are returned

Returns:

orbital parameters supported by this estimator

Throws:

OrekitException - if different parameters have the same name

getPropagationParametersDrivers

public ParameterDriversList getPropagationParametersDrivers(boolean estimatedOnly)
                                                     throws OrekitException

Get the propagator parameters supported by this estimator.

Parameters:

estimatedOnly - if true, only estimated parameters are returned

Returns:

propagator parameters supported by this estimator

Throws:

OrekitException - if different parameters have the same name

getEstimatedMeasurementsParameters

public ParameterDriversList getEstimatedMeasurementsParameters()

Get the list of estimated measurements parameters.

Returns:

the list of estimated measurements parameters

estimationStep

public NumericalPropagator[] estimationStep(ObservedMeasurement<?> observedMeasurement)
                                     throws OrekitException

Process a single measurement.

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

Parameters:

observedMeasurement - the measurement to process

Returns:

estimated propagators

Throws:

OrekitException - if an error occurred during the estimation

processMeasurements

public NumericalPropagator[] processMeasurements(Iterable<ObservedMeasurement<?>> observedMeasurements)
                                          throws OrekitException

Process several measurements.

Parameters:

observedMeasurements - the measurements to process in chronologically sorted order

Returns:

estimated propagators

Throws:

OrekitException - if an error occurred during the estimation