RelativeDistanceDetector.java
/* Copyright 2022-2024 Romain Serra
* Licensed to CS GROUP (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.orekit.propagation.events;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.hipparchus.ode.events.Action;
import org.orekit.propagation.PropagatorsParallelizer;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.handlers.EventHandler;
import org.orekit.propagation.events.handlers.StopOnEvent;
import org.orekit.utils.PVCoordinatesProvider;
/**
* Detector of specific value for the distance relative to another trajectory (using the Euclidean norm).
* <p>
* The default implementation behavior is to {@link Action#STOP stop} propagation.
* This can be changed by calling {@link #withHandler(EventHandler)} after construction.
* </p>
* <p>
* As this detector needs two objects (moving relative to each other), it embeds one
* {@link PVCoordinatesProvider coordinates provider} for the secondary object and is registered as an event detector in
* the propagator of the primary object. The secondary object {@link PVCoordinatesProvider coordinates provider} will
* therefore be driven by this detector (and hence by the propagator in which this detector is registered).
* </p>
* <p><b>
* In order to avoid infinite recursion, care must be taken to have the secondary object provider being <em>completely
* independent</em> from anything else. In particular, if the provider is a propagator, it should <em>not</em> be run
* together in a {@link PropagatorsParallelizer propagators parallelizer} with the propagator this detector is
* registered in. It is fine however to configure two separate propagators PsA and PsB with similar settings for the
* secondary object and one propagator Pm for the primary object and then use Psa in this detector registered within Pm
* while Pm and Psb are run in the context of a {@link PropagatorsParallelizer propagators parallelizer}.
* </b></p>
* <p>
* For efficiency reason during the event search loop, it is recommended to have the secondary provider be an analytical
* propagator or an ephemeris. A numerical propagator as a secondary propagator works but is expected to be
* computationally costly.
* </p>
*
* @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
* @author Romain Serra
* @since 12.1
*/
public class RelativeDistanceDetector extends AbstractDetector<RelativeDistanceDetector> {
/**
* PVCoordinates provider of the other object used to define relative distance.
*/
private final PVCoordinatesProvider secondaryPVProvider;
/** Relative distance value triggering detection. */
private final double distanceThreshold;
/**
* Constructor with default values.
* <p>
* By default, the implemented behavior is to {@link Action#STOP stop} propagation at detection.
* </p>
*
* @param secondaryPVProvider PVCoordinates provider of the other object defining relative distance.
* @param distanceThreshold Relative distance threshold for event detection
*/
public RelativeDistanceDetector(final PVCoordinatesProvider secondaryPVProvider,
final double distanceThreshold) {
this(EventDetectionSettings.getDefaultEventDetectionSettings(), new StopOnEvent(), secondaryPVProvider,
distanceThreshold);
}
/**
* Constructor.
* <p>
* This constructor is to be used if the user wants to change the default behavior of the detector.
* </p>
*
* @param detectionSettings Detection settings
* @param handler Event handler to call at event occurrences.
* @param secondaryPVProvider PVCoordinates provider of the other object defining relative distance.
* @param distanceThreshold Relative distance threshold for event detection
* @see EventHandler
* @since 12.2
*/
protected RelativeDistanceDetector(final EventDetectionSettings detectionSettings,
final EventHandler handler, final PVCoordinatesProvider secondaryPVProvider,
final double distanceThreshold) {
super(detectionSettings, handler);
this.secondaryPVProvider = secondaryPVProvider;
this.distanceThreshold = distanceThreshold;
}
/**
* Constructor.
* <p>
* This constructor is to be used if the user wants to change the default behavior of the detector.
* </p>
*
* @param maxCheck Maximum checking interval.
* @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.
* @param secondaryPVProvider PVCoordinates provider of the other object defining relative distance.
* @param distanceThreshold Relative distance threshold for event detection
* @see EventHandler
* @deprecated as of 12.2
*/
@Deprecated
protected RelativeDistanceDetector(final AdaptableInterval maxCheck, final double threshold, final int maxIter,
final EventHandler handler, final PVCoordinatesProvider secondaryPVProvider,
final double distanceThreshold) {
this(new EventDetectionSettings(maxCheck, threshold, maxIter), handler, secondaryPVProvider, distanceThreshold);
}
/**
* The {@code g} is positive when the relative distance is larger or equal than the threshold,
* non-positive otherwise.
*
* @param s the current state information: date, kinematics, attitude
* @return value of the switching function
*/
public double g(final SpacecraftState s) {
final Vector3D secondaryPosition = getSecondaryPVProvider().getPosition(s.getDate(), s.getFrame());
final double relativeDistance = s.getPosition().subtract(secondaryPosition).getNorm();
return relativeDistance - distanceThreshold;
}
/** {@inheritDoc} */
@Override
protected RelativeDistanceDetector create(final AdaptableInterval newMaxCheck, final double newThreshold,
final int newMaxIter, final EventHandler newHandler) {
return new RelativeDistanceDetector(newMaxCheck, newThreshold, newMaxIter, newHandler, secondaryPVProvider,
distanceThreshold);
}
/**
* Get the secondary position-velocity provider stored in this instance.
*
* @return the secondary position-velocity provider stored in this instance
*/
public PVCoordinatesProvider getSecondaryPVProvider() {
return secondaryPVProvider;
}
/**
* Get the relative distance threshold.
*
* @return threshold triggering detection
*/
public double getDistanceThreshold() {
return distanceThreshold;
}
}