LongitudeExtremumDetector.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.analysis.differentiation.DerivativeStructure;
import org.orekit.bodies.BodyShape;
import org.orekit.bodies.FieldGeodeticPoint;
import org.orekit.bodies.OneAxisEllipsoid;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.handlers.EventHandler;
import org.orekit.propagation.events.handlers.StopOnIncreasing;
/** Detector for geographic longitude extremum.
* <p>This detector identifies when a spacecraft reaches its
* extremum longitudes with respect to a central body.</p>
* @author Luc Maisonobe
* @since 7.1
*/
public class LongitudeExtremumDetector extends AbstractDetector<LongitudeExtremumDetector> {
/** Body on which the longitude is defined. */
private OneAxisEllipsoid body;
/** Build a new detector.
* <p>The new instance uses default values for maximal checking interval
* ({@link #DEFAULT_MAXCHECK}) and convergence threshold ({@link
* #DEFAULT_THRESHOLD}).</p>
* @param body body on which the longitude is defined
*/
public LongitudeExtremumDetector(final OneAxisEllipsoid body) {
this(DEFAULT_MAXCHECK, DEFAULT_THRESHOLD, body);
}
/** Build a detector.
* @param maxCheck maximal checking interval (s)
* @param threshold convergence threshold (s)
* @param body body on which the longitude is defined
*/
public LongitudeExtremumDetector(final double maxCheck, final double threshold,
final OneAxisEllipsoid body) {
this(maxCheck, threshold, DEFAULT_MAX_ITER, new StopOnIncreasing<LongitudeExtremumDetector>(),
body);
}
/** 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
* @param body body on which the longitude is defined
*/
private LongitudeExtremumDetector(final double maxCheck, final double threshold,
final int maxIter, final EventHandler<? super LongitudeExtremumDetector> handler,
final OneAxisEllipsoid body) {
super(maxCheck, threshold, maxIter, handler);
this.body = body;
}
/** {@inheritDoc} */
@Override
protected LongitudeExtremumDetector create(final double newMaxCheck, final double newThreshold,
final int newMaxIter,
final EventHandler<? super LongitudeExtremumDetector> newHandler) {
return new LongitudeExtremumDetector(newMaxCheck, newThreshold, newMaxIter, newHandler, body);
}
/** Get the body on which the geographic zone is defined.
* @return body on which the geographic zone is defined
*/
public BodyShape getBody() {
return body;
}
/** Compute the value of the detection function.
* <p>
* The value is the spacecraft longitude time derivative.
* </p>
* @param s the current state information: date, kinematics, attitude
* @return spacecraft longitude time derivative
*/
public double g(final SpacecraftState s) {
// convert state to geodetic coordinates
final FieldGeodeticPoint<DerivativeStructure> gp =
body.transform(s.getPVCoordinates(), s.getFrame(), s.getDate());
// longitude time derivative
return gp.getLongitude().getPartialDerivative(1);
}
}