org.orekit.propagation.numerical

Class PartialDerivativesEquations

java.lang.Object

org.orekit.propagation.numerical.PartialDerivativesEquations

All Implemented Interfaces:

AdditionalEquations

public class PartialDerivativesEquations
extends Object
implements AdditionalEquations

Set of additional equations computing the partial derivatives of the state (orbit) with respect to initial state and force models parameters.

This set of equations are automatically added to a numerical propagator in order to compute partial derivatives of the orbit along with the orbit itself. This is useful for example in orbit determination applications.

Author:

Véronique Pommier-Maurussane

Constructor Summary

Constructors

Constructor and Description
PartialDerivativesEquations(String name, NumericalPropagator propagator) Simple constructor.

Method Summary

Methods

Modifier and Type	Method and Description
double[]	computeDerivatives(SpacecraftState s, double[] pDot) Compute the derivatives related to the additional state parameters.
List<String>	getAvailableParameters() Get the names of the available parameters in the propagator.
JacobiansMapper	getMapper() Get a mapper between two-dimensional Jacobians and one-dimensional additional state.
String	getName() Get the name of the additional state.
void	selectParamAndStep(String parameter, double hP) Select the parameters to consider for Jacobian processing.
void	selectParameters(String... parameters) Select the parameters to consider for Jacobian processing.
SpacecraftState	setInitialJacobians(SpacecraftState s1, double[][] dY1dY0, double[][] dY1dP) Set the initial value of the Jacobian with respect to state and parameter.
SpacecraftState	setInitialJacobians(SpacecraftState s0, int stateDimension, int paramDimension) Set the initial value of the Jacobian with respect to state and parameter.

Methods inherited from class java.lang.Object

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

Constructor Detail

PartialDerivativesEquations

public PartialDerivativesEquations(String name,
                           NumericalPropagator propagator)
                            throws OrekitException

Simple constructor.

Upon construction, this set of equations is automatically added to the propagator by calling its AbstractIntegratedPropagator.addAdditionalEquations(AdditionalEquations) method. So there is no need to call this method explicitly for these equations.

Parameters:

name - name of the partial derivatives equations

propagator - the propagator that will handle the orbit propagation

Throws:

OrekitException - if a set of equations with the same name is already present

Method Detail

getName

public String getName()

Get the name of the additional state.

Specified by:

getName in interface AdditionalEquations

Returns:

name of the additional state

getAvailableParameters

public List<String> getAvailableParameters()

Get the names of the available parameters in the propagator.

The names returned depend on the force models set up in the propagator, including the Newtonian attraction from the central body.

Returns:

available parameters

selectParameters

public void selectParameters(String... parameters)

Select the parameters to consider for Jacobian processing.

Parameters names have to be consistent with some ForceModel added elsewhere.

Parameters:

parameters - parameters to consider for Jacobian processing

See Also:

NumericalPropagator.addForceModel(ForceModel), setInitialJacobians(SpacecraftState, double[][], double[][]), ForceModel, Parameterizable

selectParamAndStep

public void selectParamAndStep(String parameter,
                      double hP)

Select the parameters to consider for Jacobian processing.

Parameters names have to be consistent with some ForceModel added elsewhere.

Parameters:

parameter - parameter to consider for Jacobian processing

hP - step to use for computing Jacobian column with respect to the specified parameter

See Also:

NumericalPropagator.addForceModel(ForceModel), setInitialJacobians(SpacecraftState, double[][], double[][]), ForceModel, Parameterizable

setInitialJacobians

public SpacecraftState setInitialJacobians(SpacecraftState s0,
                                  int stateDimension,
                                  int paramDimension)
                                    throws OrekitException

Set the initial value of the Jacobian with respect to state and parameter.

This method is equivalent to call setInitialJacobians(SpacecraftState, double[][], double[][]) with dYdY0 set to the identity matrix and dYdP set to a zero matrix.

The returned state must be added to the propagator (it is not done automatically, as the user may need to add more states to it).

Parameters:

s0 - initial state

stateDimension - state dimension, must be either 6 for orbit only or 7 for orbit and mass

paramDimension - parameters dimension

Returns:

state with initial Jacobians added

Throws:

OrekitException - if the partial equation has not been registered in the propagator or if matrices dimensions are incorrect

See Also:

selectedParameters, selectParamAndStep(String, double)

setInitialJacobians

public SpacecraftState setInitialJacobians(SpacecraftState s1,
                                  double[][] dY1dY0,
                                  double[][] dY1dP)
                                    throws OrekitException

Set the initial value of the Jacobian with respect to state and parameter.

The returned state must be added to the propagator (it is not done automatically, as the user may need to add more states to it).

Parameters:

s1 - current state

dY1dY0 - Jacobian of current state at time t₁ with respect to state at some previous time t₀ (may be either 6x6 for orbit only or 7x7 for orbit and mass)

dY1dP - Jacobian of current state at time t₁ with respect to parameters (may be null if no parameters are selected)

Returns:

state with initial Jacobians added

Throws:

OrekitException - if the partial equation has not been registered in the propagator or if matrices dimensions are incorrect

See Also:

selectedParameters, selectParamAndStep(String, double)

getMapper

public JacobiansMapper getMapper()
                          throws OrekitException

Get a mapper between two-dimensional Jacobians and one-dimensional additional state.

Returns:

a mapper between two-dimensional Jacobians and one-dimensional additional state, with the same name as the instance

Throws:

OrekitException - if the initial Jacobians have not been initialized yet

See Also:

setInitialJacobians(SpacecraftState, int, int), setInitialJacobians(SpacecraftState, double[][], double[][])

computeDerivatives

public double[] computeDerivatives(SpacecraftState s,
                          double[] pDot)
                            throws OrekitException

Compute the derivatives related to the additional state parameters.

When this method is called, the spacecraft state contains the main state (orbit, attitude and mass), all the states provided through the additional state providers registered to the propagator, and the additional state integrated using this equation. It does not contains any other states to be integrated alongside during the same propagation.

Specified by:

computeDerivatives in interface AdditionalEquations

Parameters:

s - current state information: date, kinematics, attitude, and additional state

pDot - placeholder where the derivatives of the additional parameters should be put

Returns:

cumulative effect of the equations on the main state (may be null if equations do not change main state at all)

Throws:

OrekitException - if some specific error occurs