org.orekit.estimation.sequential

Class SemiAnalyticalKalmanEstimator

java.lang.Object

org.orekit.estimation.sequential.SemiAnalyticalKalmanEstimator

public class SemiAnalyticalKalmanEstimator
extends Object

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

Method Summary

Modifier and Type	Method and Description
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.
DSSTPropagator	processMeasurements(List<ObservedMeasurement<?>> observedMeasurements) Process a single measurement.
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

Constructor Detail

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 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)

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

getPropagationParametersDrivers

public ParameterDriversList getPropagationParametersDrivers(boolean estimatedOnly)

Get the propagator parameters supported by this estimator.

Parameters:

estimatedOnly - if true, only estimated parameters are returned

Returns:

propagator parameters supported by this estimator

getEstimatedMeasurementsParameters

public ParameterDriversList getEstimatedMeasurementsParameters()

Get the list of estimated measurements parameters.

Returns:

the list of estimated measurements parameters

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