Propagator.java
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package org.orekit.propagation;
import java.util.Collection;
import java.util.List;
import org.hipparchus.geometry.euclidean.threed.Rotation;
import org.hipparchus.linear.RealMatrix;
import org.orekit.attitudes.AttitudeProvider;
import org.orekit.attitudes.FrameAlignedProvider;
import org.orekit.frames.Frame;
import org.orekit.frames.Frames;
import org.orekit.orbits.PositionAngleType;
import org.orekit.propagation.events.EventDetector;
import org.orekit.propagation.sampling.OrekitFixedStepHandler;
import org.orekit.propagation.sampling.OrekitStepHandler;
import org.orekit.propagation.sampling.StepHandlerMultiplexer;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.DoubleArrayDictionary;
import org.orekit.utils.PVCoordinatesProvider;
/** This interface provides a way to propagate an orbit at any time.
*
* <p>This interface is the top-level abstraction for orbit propagation.
* It only allows propagation to a predefined date.
* It is implemented by analytical models which have no time limit,
* by orbit readers based on external data files, by numerical integrators
* using rich force models and by continuous models built after numerical
* integration has been completed and dense output data as been
* gathered.</p>
* <p>Note that one single propagator cannot be called from multiple threads.
* Its configuration can be changed as there is at least a {@link
* #resetInitialState(SpacecraftState)} method, and even propagators that do
* not support resetting state (like the {@link
* org.orekit.propagation.analytical.tle.TLEPropagator TLEPropagator} do
* cache some internal data during computation. However, as long as they
* are configured with independent building blocks (mainly event handlers
* and step handlers that may preserve some internal state), and as long
* as they are called from one thread only, they <em>can</em> be used in
* multi-threaded applications. Synchronizing several propagators to run in
* parallel is also possible using {@link PropagatorsParallelizer}.</p>
* @author Luc Maisonobe
* @author Véronique Pommier-Maurussane
*
*/
public interface Propagator extends PVCoordinatesProvider {
/** Default mass. */
double DEFAULT_MASS = 1000.0;
/**
* Get a default law using the given frames.
*
* @param frames the set of frames to use.
* @return attitude law.
*/
static AttitudeProvider getDefaultLaw(final Frames frames) {
return new FrameAlignedProvider(Rotation.IDENTITY, frames.getEME2000());
}
/** Get the multiplexer holding all step handlers.
* @return multiplexer holding all step handlers
* @since 11.0
*/
StepHandlerMultiplexer getMultiplexer();
/** Remove all step handlers.
* <p>This convenience method is equivalent to call {@code getMultiplexer().clear()}</p>
* @see #getMultiplexer()
* @see StepHandlerMultiplexer#clear()
* @since 11.0
*/
default void clearStepHandlers() {
getMultiplexer().clear();
}
/** Set a single handler for fixed stepsizes.
* <p>This convenience method is equivalent to call {@code getMultiplexer().clear()}
* followed by {@code getMultiplexer().add(h, handler)}</p>
* @param h fixed stepsize (s)
* @param handler handler called at the end of each finalized step
* @see #getMultiplexer()
* @see StepHandlerMultiplexer#add(double, OrekitFixedStepHandler)
* @since 11.0
*/
default void setStepHandler(final double h, final OrekitFixedStepHandler handler) {
getMultiplexer().clear();
getMultiplexer().add(h, handler);
}
/** Set a single handler for variable stepsizes.
* <p>This convenience method is equivalent to call {@code getMultiplexer().clear()}
* followed by {@code getMultiplexer().add(handler)}</p>
* @param handler handler called at the end of each finalized step
* @see #getMultiplexer()
* @see StepHandlerMultiplexer#add(OrekitStepHandler)
* @since 11.0
*/
default void setStepHandler(final OrekitStepHandler handler) {
getMultiplexer().clear();
getMultiplexer().add(handler);
}
/**
* Set up an ephemeris generator that will monitor the propagation for building
* an ephemeris from it once completed.
*
* <p>
* This generator can be used when the user needs fast random access to the orbit
* state at any time between the initial and target times. A typical example is the
* implementation of search and iterative algorithms that may navigate forward and
* backward inside the propagation range before finding their result even if the
* propagator used is integration-based and only goes from one initial time to one
* target time.
* </p>
* <p>
* Beware that when used with integration-based propagators, the generator will
* store <strong>all</strong> intermediate results. It is therefore memory intensive
* for long integration-based ranges and high precision/short time steps. When
* used with analytical propagators, the generator only stores start/stop time
* and a reference to the analytical propagator itself to call it back as needed,
* so it is less memory intensive.
* </p>
* <p>
* The returned ephemeris generator will be initially empty, it will be filled
* with propagation data when a subsequent call to either {@link #propagate(AbsoluteDate)
* propagate(target)} or {@link #propagate(AbsoluteDate, AbsoluteDate)
* propagate(start, target)} is called. The proper way to use this method is
* therefore to do:
* </p>
* <pre>
* EphemerisGenerator generator = propagator.getEphemerisGenerator();
* propagator.propagate(target);
* BoundedPropagator ephemeris = generator.getGeneratedEphemeris();
* </pre>
* @return ephemeris generator
*/
EphemerisGenerator getEphemerisGenerator();
/** Get the propagator initial state.
* @return initial state
*/
SpacecraftState getInitialState();
/** Reset the propagator initial state.
* @param state new initial state to consider
*/
void resetInitialState(SpacecraftState state);
/** Add a set of user-specified state parameters to be computed along with the orbit propagation.
* @param additionalStateProvider provider for additional state
*/
void addAdditionalStateProvider(AdditionalStateProvider additionalStateProvider);
/** Get an unmodifiable list of providers for additional state.
* @return providers for the additional states
*/
List<AdditionalStateProvider> getAdditionalStateProviders();
/** Check if an additional state is managed.
* <p>
* Managed states are states for which the propagators know how to compute
* its evolution. They correspond to additional states for which a
* {@link AdditionalStateProvider provider} has been registered by calling the
* {@link #addAdditionalStateProvider(AdditionalStateProvider) addAdditionalStateProvider} method.
* </p>
* <p>
* Additional states that are present in the {@link #getInitialState() initial state}
* but have no evolution method registered are <em>not</em> considered as managed states.
* These unmanaged additional states are not lost during propagation, though. Their
* value are piecewise constant between state resets that may change them if some
* event handler {@link
* org.orekit.propagation.events.handlers.EventHandler#resetState(EventDetector,
* SpacecraftState) resetState} method is called at an event occurrence and happens
* to change the unmanaged additional state.
* </p>
* @param name name of the additional state
* @return true if the additional state is managed
*/
boolean isAdditionalStateManaged(String name);
/** Get all the names of all managed states.
* @return names of all managed states
*/
String[] getManagedAdditionalStates();
/** Add an event detector.
* @param detector event detector to add
* @see #clearEventsDetectors()
* @see #getEventsDetectors()
* @param <T> class type for the generic version
*/
<T extends EventDetector> void addEventDetector(T detector);
/** Get all the events detectors that have been added.
* @return an unmodifiable collection of the added detectors
* @see #addEventDetector(EventDetector)
* @see #clearEventsDetectors()
*/
Collection<EventDetector> getEventsDetectors();
/** Remove all events detectors.
* @see #addEventDetector(EventDetector)
* @see #getEventsDetectors()
*/
void clearEventsDetectors();
/** Get attitude provider.
* @return attitude provider
*/
AttitudeProvider getAttitudeProvider();
/** Set attitude provider.
* @param attitudeProvider attitude provider
*/
void setAttitudeProvider(AttitudeProvider attitudeProvider);
/** Get the frame in which the orbit is propagated.
* <p>
* The propagation frame is the definition frame of the initial
* state, so this method should be called after this state has
* been set, otherwise it may return null.
* </p>
* @return frame in which the orbit is propagated
* @see #resetInitialState(SpacecraftState)
*/
Frame getFrame();
/** Set up computation of State Transition Matrix and Jacobians matrix with respect to parameters.
* <p>
* If this method is called, both State Transition Matrix and Jacobians with respect to the
* force models parameters that will be selected when propagation starts will be automatically
* computed, and the harvester will allow to retrieve them.
* </p>
* <p>
* The arguments for initial matrices <em>must</em> be compatible with the {@link org.orekit.orbits.OrbitType
* orbit type} and {@link PositionAngleType position angle} that will be used by the propagator.
* </p>
* <p>
* The default implementation throws an exception as the method is not supported by all propagators.
* </p>
* @param stmName State Transition Matrix state name
* @param initialStm initial State Transition Matrix ∂Y/∂Y₀,
* if null (which is the most frequent case), assumed to be 6x6 identity
* @param initialJacobianColumns initial columns of the Jacobians matrix with respect to parameters,
* if null or if some selected parameters are missing from the dictionary, the corresponding
* initial column is assumed to be 0
* @return harvester to retrieve computed matrices during and after propagation
* @since 11.1
*/
default MatricesHarvester setupMatricesComputation(final String stmName, final RealMatrix initialStm,
final DoubleArrayDictionary initialJacobianColumns) {
throw new UnsupportedOperationException();
}
/** Propagate towards a target date.
* <p>Simple propagators use only the target date as the specification for
* computing the propagated state. More feature rich propagators can consider
* other information and provide different operating modes or G-stop
* facilities to stop at pinpointed events occurrences. In these cases, the
* target date is only a hint, not a mandatory objective.</p>
* @param target target date towards which orbit state should be propagated
* @return propagated state
*/
SpacecraftState propagate(AbsoluteDate target);
/** Propagate from a start date towards a target date.
* <p>Those propagators use a start date and a target date to
* compute the propagated state. For propagators using event detection mechanism,
* if the provided start date is different from the initial state date, a first,
* simple propagation is performed, without processing any event computation.
* Then complete propagation is performed from start date to target date.</p>
* @param start start date from which orbit state should be propagated
* @param target target date to which orbit state should be propagated
* @return propagated state
*/
SpacecraftState propagate(AbsoluteDate start, AbsoluteDate target);
}