Package org.orekit.propagation.numerical

Class EpochDerivativesEquations

  • All Implemented Interfaces:
    AdditionalDerivativesProvider
    public class EpochDerivativesEquations
extends Object
implements AdditionalDerivativesProvider
    Computes derivatives of the acceleration, including ThirdBodyAttraction. Provider 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.

    The partial derivatives with respect to initial state can be either dimension 6 (orbit only) or 7 (orbit and mass).

    The partial derivatives with respect to force models parameters has a dimension equal to the number of selected parameters. Parameters selection is implemented at force models level. Users must retrieve a parameter driver using ParameterDriversProvider.getParameterDriver(String) and then select it by calling setSelected(true).

    If several force models provide different drivers for the same parameter name, selecting any of these drivers has the side effect of selecting all the drivers for this shared parameter. In this case, the partial derivatives will be the sum of the partial derivatives contributed by the corresponding force models. This case typically arises for central attraction coefficient, which has an influence on Newtonian attraction, gravity field, and relativity.

    Since:
    10.2
    Author:
    Véronique Pommier-Maurussane, Luc Maisonobe

    • Field Detail

      • STATE_DIMENSION

        public static final int STATE_DIMENSION
        State dimension, fixed to 6.
        See Also:
        Constant Field Values

    • Method Detail

      • getName

        public String getName()
        Get the name of the additional derivatives (which will become state once integrated).
        Specified by:
        getName in interface AdditionalDerivativesProvider
        Returns:
        name of the additional state (names containing "orekit" with any case are reserved for the library internal use)

      • setInitialJacobians

        public SpacecraftState setInitialJacobians​(SpacecraftState s0)
        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 force models parameters for which partial derivatives are desired, must have been selected before this method is called, so proper matrices dimensions are used.

        Parameters:
        s0 - initial state
        Returns:
        state with initial Jacobians added

      • setInitialJacobians

        public SpacecraftState setInitialJacobians​(SpacecraftState s1,
                                           double[][] dY1dY0,
                                           double[][] dY1dP)
        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).

        The force models parameters for which partial derivatives are desired, must have been selected before this method is called, and the dY1dP matrix dimension must be consistent with the selection.

        Parameters:
        s1 - current state
        dY1dY0 - Jacobian of current state at time t₁ with respect to state at some previous time t₀ (must be 6x6)
        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

      • setInitialJacobians

        public void setInitialJacobians​(SpacecraftState state,
                                double[][] dY1dY0,
                                double[][] dY1dP,
                                double[] p)
        Set the Jacobian with respect to state into a one-dimensional additional state array.

        This method converts the Jacobians to Cartesian parameters and put the converted data in the one-dimensional p array.

        Parameters:
        state - spacecraft state
        dY1dY0 - Jacobian of current state at time t₁ with respect to state at some previous time t₀
        dY1dP - Jacobian of current state at time t₁ with respect to parameters (may be null if there are no parameters)
        p - placeholder where to put the one-dimensional additional state

      • combinedDerivatives

        public CombinedDerivatives combinedDerivatives​(SpacecraftState s)
        Compute the derivatives related to the additional state (and optionally main state increments).
        Specified by:
        combinedDerivatives in interface AdditionalDerivativesProvider
        Parameters:
        s - current state information: date, kinematics, attitude, and additional states this equations depend on (according to the yields method)
        Returns:
        computed combined derivatives, which may include some incremental coupling effect to add to main state derivatives