ApsideDetector.java
/* Copyright 2002-2022 CS GROUP
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* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
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*
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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.geometry.euclidean.threed.Vector3D;
import org.hipparchus.ode.events.Action;
import org.orekit.orbits.Orbit;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.handlers.EventHandler;
import org.orekit.propagation.events.handlers.StopOnIncreasing;
import org.orekit.utils.PVCoordinates;
/** Finder for apside crossing events.
* <p>This class finds apside crossing events (i.e. apogee or perigee crossing).</p>
* <p>The default implementation behavior is to {@link Action#CONTINUE continue}
* propagation at apogee crossing and to {@link Action#STOP stop} propagation
* at perigee crossing. This can be changed by calling
* {@link #withHandler(EventHandler)} after construction.</p>
* <p>Beware that apside detection will fail for almost circular orbits. If
* for example an apside detector is used to trigger an {@link
* org.orekit.forces.maneuvers.ImpulseManeuver ImpulseManeuver} and the maneuver
* change the orbit shape to circular, then the detector may completely fail just
* after the maneuver has been performed!</p>
* @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
* @author Luc Maisonobe
*/
public class ApsideDetector extends AbstractDetector<ApsideDetector> {
/** Build a new instance.
* <p>The orbit is used only to set an upper bound for the
* max check interval to period/3 and to set the convergence
* threshold according to orbit size</p>
* @param orbit initial orbit
*/
public ApsideDetector(final Orbit orbit) {
this(1.0e-13 * orbit.getKeplerianPeriod(), orbit);
}
/** Build a new instance.
* <p>The orbit is used only to set an upper bound for the
* max check interval to period/3</p>
* @param threshold convergence threshold (s)
* @param orbit initial orbit
*/
public ApsideDetector(final double threshold, final Orbit orbit) {
super(orbit.getKeplerianPeriod() / 3, threshold,
DEFAULT_MAX_ITER, new StopOnIncreasing<ApsideDetector>());
}
/** Private constructor with full parameters.
* <p>
* This constructor is private as users are expected to use the builder
* API with the various {@code withXxx()} methods to set up the instance
* in a readable manner without using a huge amount of parameters.
* </p>
* @param maxCheck maximum checking interval (s)
* @param threshold convergence threshold (s)
* @param maxIter maximum number of iterations in the event time search
* @param handler event handler to call at event occurrences
* @since 6.1
*/
private ApsideDetector(final double maxCheck, final double threshold,
final int maxIter, final EventHandler<? super ApsideDetector> handler) {
super(maxCheck, threshold, maxIter, handler);
}
/** {@inheritDoc} */
@Override
protected ApsideDetector create(final double newMaxCheck, final double newThreshold,
final int newMaxIter, final EventHandler<? super ApsideDetector> newHandler) {
return new ApsideDetector(newMaxCheck, newThreshold, newMaxIter, newHandler);
}
/** Compute the value of the switching function.
* This function computes the dot product of the 2 vectors : position.velocity.
* @param s the current state information: date, kinematics, attitude
* @return value of the switching function
*/
public double g(final SpacecraftState s) {
final PVCoordinates pv = s.getPVCoordinates();
return Vector3D.dotProduct(pv.getPosition(), pv.getVelocity());
}
}