org.orekit.propagation.integration

Interface AdditionalDerivativesProvider

All Known Implementing Classes:

AbsolutePartialDerivativesEquations, AdditionalEquationsAdapter, DSSTPartialDerivativesEquations, EpochDerivativesEquations, MassDepletionDelay, PartialDerivativesEquations, STMEquations

public interface AdditionalDerivativesProvider

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 AbstractIntegratedPropagator.addAdditionalDerivativesProvider(AdditionalDerivativesProvider) 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 AdditionalStateProvider interface. It allows to append various additional state parameters to any numerical propagator or DSST propagator.

Since:

11.1

Author:

Luc Maisonobe

See Also:

AbstractIntegratedPropagator

Method Summary

Modifier and Type	Method and Description
double[]	derivatives(SpacecraftState s) Compute the derivatives related to the additional state parameters.
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(SpacecraftState initialState, AbsoluteDate target) Initialize the generator at the start of propagation.
default boolean	yield(SpacecraftState 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(SpacecraftState initialState,
                  AbsoluteDate 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(SpacecraftState 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 SpacecraftState 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

double[] derivatives(SpacecraftState s)

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