org.orekit.propagation.integration

Interface FieldAdditionalDerivativesProvider<T extends CalculusFieldElement<T>>

All Known Implementing Classes:

FieldAdditionalEquationsAdapter

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 Summary

Modifier and Type	Method and Description
default FieldCombinedDerivatives<T>	combinedDerivatives(FieldSpacecraftState<T> s) Compute the derivatives related to the additional state (and optionally main state increments).
T[]	derivatives(FieldSpacecraftState<T> s) Deprecated. as of 11.2, replaced by combinedDerivatives(FieldSpacecraftState)
int	getDimension() Get the dimension of the generated derivative.
String	getName() Get the name of the additional derivatives (which will become state once integrated).
default void	init(FieldSpacecraftState<T> initialState, FieldAbsoluteDate<T> target) Initialize the generator at the start of propagation.
default boolean	yield(FieldSpacecraftState<T> state) Check if this provider should yield so another provider has an opportunity to add missing parts.

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

yield

default boolean yield(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 yield(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

derivatives

@Deprecated
T[] derivatives(FieldSpacecraftState<T> s)

Deprecated. as of 11.2, replaced by combinedDerivatives(FieldSpacecraftState)

Compute the derivatives related to the additional state parameters.

Parameters:

s - current state information: date, kinematics, attitude, and additional states this equations depend on (according to the yield method)

Returns:

computed derivatives

combinedDerivatives

default FieldCombinedDerivatives<T> combinedDerivatives(FieldSpacecraftState<T> s)

Compute the derivatives related to the additional state (and optionally main state increments).

As of 11.2, there is a default implementation that calls the deprecated derivatives(FieldSpacecraftState) method. This has been done for backward compatibility only and will be removed in 12.0.

Parameters:

s - current state information: date, kinematics, attitude, and additional states this equations depend on (according to the yield method)

Returns:

computed combined derivatives, which may include some incremental coupling effect to add to main state derivatives

Since:

11.2