Package org.orekit.propagation.integration

Interface FieldAdditionalDerivativesProvider<T extends CalculusFieldElement<T>>

  • Type Parameters:
    T - type of the field elements
    public interface FieldAdditionalDerivativesProvider<T extends CalculusFieldElement<T>>
    Provider for additional derivatives.

    In some cases users may need to integrate some problem-specific equations along with classical spacecraft equations of motions. One example is optimal control in low thrust where adjoint parameters linked to the minimized Hamiltonian must be integrated. Another example is formation flying or rendez-vous which use the Clohessy-Whiltshire equations for the relative motion.

    This interface allows users to add such equations to a numerical propagator or a DSST propagator. Users provide the equations as an implementation of this interface and register it to the propagator thanks to its FieldAbstractIntegratedPropagator.addAdditionalDerivativesProvider(FieldAdditionalDerivativesProvider) method. Several such objects can be registered with each numerical propagator, but it is recommended to gather in the same object the sets of parameters which equations can interact on each others states.

    This interface is the numerical (read not already integrated) counterpart of the FieldAdditionalStateProvider interface. It allows to append various additional state parameters to any numerical propagator or DSST propagator.

    Since:
    11.1
    Author:
    Luc Maisonobe
    See Also:
    FieldAbstractIntegratedPropagator

    • Method Detail

      • getName

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

      • getDimension

        int getDimension()
        Get the dimension of the generated derivative.
        Returns:
        dimension of the generated

      • init

        default void init​(FieldSpacecraftState<T> initialState,
                  FieldAbsoluteDate<T> target)
        Initialize the generator at the start of propagation.
        Parameters:
        initialState - initial state information at the start of propagation
        target - date of propagation

      • yields

        default boolean yields​(FieldSpacecraftState<T> state)
        Check if this provider should yield so another provider has an opportunity to add missing parts.

        Decision to yield is often based on an additional state being already available in the provided state (but it could theoretically also depend on an additional state derivative being already available, or any other criterion). If for example a provider needs the state transition matrix, it could implement this method as: 

        
 public boolean yields(final FieldSpacecraftState<T> state) {
     return !state.getAdditionalStates().containsKey("STM");
 }

        The default implementation returns false, meaning that derivative data can be computed immediately.

        Parameters:
        state - state to handle
        Returns:
        true if this provider should yield so another provider has an opportunity to add missing parts as the state is incrementally built up

      • combinedDerivatives

        FieldCombinedDerivatives<T> combinedDerivatives​(FieldSpacecraftState<T> s)
        Compute the derivatives related to the additional state (and optionally main state increments).
        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
        Since:
        11.2