FieldEventDetector.java
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* Unless required by applicable law or agreed to in writing, software
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package org.orekit.propagation.events;
import org.hipparchus.CalculusFieldElement;
import org.hipparchus.ode.events.Action;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.time.FieldAbsoluteDate;
/** This interface represents space-dynamics aware events detectors.
*
* <p>It mirrors the {@link org.hipparchus.ode.events.FieldODEEventHandler
* FieldODEEventHandler} interface from <a href="https://hipparchus.org/">
* Hipparchus</a> but provides a space-dynamics interface to the
* methods.</p>
*
* <p>Events detectors are a useful solution to meet the requirements
* of propagators concerning discrete conditions. The state of each
* event detector is queried by the integrator at each step. When the
* sign of the underlying g switching function changes, the step is rejected
* and reduced, in order to make sure the sign changes occur only at steps
* boundaries.</p>
*
* <p>When step ends exactly at a switching function sign change, the corresponding
* event is triggered, by calling the {@link #eventOccurred(FieldSpacecraftState, boolean)}
* method. The method can do whatever it needs with the event (logging it, performing
* some processing, ignore it ...). The return value of the method will be used by
* the propagator to stop or resume propagation, possibly changing the state vector.<p>
*
* @author Luc Maisonobe
* @author Véronique Pommier-Maurussane
*/
public interface FieldEventDetector <T extends CalculusFieldElement<T>> {
/** Initialize event handler at the start of a propagation.
* <p>
* This method is called once at the start of the propagation. It
* may be used by the event handler to initialize some internal data
* if needed.
* </p>
* <p>
* The default implementation does nothing
* </p>
* @param s0 initial state
* @param t target time for the integration
*
*/
default void init(FieldSpacecraftState<T> s0,
FieldAbsoluteDate<T> t) {
// nothing by default
}
/** Compute the value of the switching function.
* This function must be continuous (at least in its roots neighborhood),
* as the integrator will need to find its roots to locate the events.
* @param s the current state information: date, kinematics, attitude
* @return value of the switching function
*/
T g(FieldSpacecraftState<T> s);
/** Get the convergence threshold in the event time search.
* @return convergence threshold (s)
*/
T getThreshold();
/** Get maximal time interval between switching function checks.
* @return maximal time interval (s) between switching function checks
*/
T getMaxCheckInterval();
/** Get maximal number of iterations in the event time search.
* @return maximal number of iterations in the event time search
*/
int getMaxIterationCount();
/** Handle the event.
* @param s SpaceCraft state to be used in the evaluation
* @param increasing with the event occurred in an "increasing" or "decreasing" slope direction
* @return the Action that the calling detector should pass back to the evaluation system
* @since 7.0
*/
Action eventOccurred(FieldSpacecraftState<T> s, boolean increasing);
/** Reset the state prior to continue propagation.
* <p>This method is called after the step handler has returned and
* before the next step is started, but only when {@link
* #eventOccurred} has itself returned the {@link Action#RESET_STATE}
* indicator. It allows the user to reset the state for the next step,
* without perturbing the step handler of the finishing step. If the
* {@link #eventOccurred} never returns the {@link Action#RESET_STATE}
* indicator, this function will never be called, and it is safe to simply return null.</p>
* <p>
* The default implementation simply returns its argument.
* </p>
* @param oldState old state
* @return new state
* @since 7.0
*/
default FieldSpacecraftState<T> resetState(FieldSpacecraftState<T> oldState) {
return oldState;
}
}