/* Copyright 2002-2017 CS Systèmes d'Information
* Licensed to CS Systèmes d'Information (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.util.FastMath;
import org.orekit.errors.OrekitException;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.handlers.EventHandler;
import org.orekit.propagation.events.handlers.StopOnIncreasing;
import org.orekit.utils.PVCoordinatesProvider;
/** Finder for satellite eclipse related events.
* <p>This class finds eclipse events, i.e. satellite within umbra (total
* eclipse) or penumbra (partial eclipse).</p>
* <p>The default implementation behavior is to {@link
* org.orekit.propagation.events.handlers.EventHandler.Action#CONTINUE continue}
* propagation when entering the eclipse and to {@link
* org.orekit.propagation.events.handlers.EventHandler.Action#STOP stop} propagation
* when exiting the eclipse. This can be changed by calling {@link
* #withHandler(EventHandler)} after construction.</p>
* @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
* @author Pascal Parraud
*/
public class EclipseDetector extends AbstractDetector<EclipseDetector> {
/** Serializable UID. */
private static final long serialVersionUID = 20131118L;
/** Occulting body. */
private final PVCoordinatesProvider occulting;
/** Occulting body radius (m). */
private final double occultingRadius;
/** Occulted body. */
private final PVCoordinatesProvider occulted;
/** Occulted body radius (m). */
private final double occultedRadius;
/** Umbra, if true, or penumbra, if false, detection flag. */
private boolean totalEclipse;
/** Build a new eclipse detector.
* <p>The new instance is a total eclipse (umbra) detector with default
* values for maximal checking interval ({@link #DEFAULT_MAXCHECK})
* and convergence threshold ({@link #DEFAULT_THRESHOLD}).</p>
* @param occulted the body to be occulted
* @param occultedRadius the radius of the body to be occulted (m)
* @param occulting the occulting body
* @param occultingRadius the occulting body radius (m)
*/
public EclipseDetector(final PVCoordinatesProvider occulted, final double occultedRadius,
final PVCoordinatesProvider occulting, final double occultingRadius) {
this(DEFAULT_MAXCHECK, DEFAULT_THRESHOLD,
occulted, occultedRadius, occulting, occultingRadius);
}
/** Build a new eclipse detector.
* <p>The new instance is a total eclipse (umbra) detector with default
* value for convergence threshold ({@link #DEFAULT_THRESHOLD}).</p>
* <p>The maximal interval between eclipse checks should be smaller than
* the half duration of the minimal pass to handle, otherwise some short
* passes could be missed.</p>
* @param maxCheck maximal checking interval (s)
* @param occulted the body to be occulted
* @param occultedRadius the radius of the body to be occulted in meters
* @param occulting the occulting body
* @param occultingRadius the occulting body radius in meters
*/
public EclipseDetector(final double maxCheck,
final PVCoordinatesProvider occulted, final double occultedRadius,
final PVCoordinatesProvider occulting, final double occultingRadius) {
this(maxCheck, DEFAULT_THRESHOLD,
occulted, occultedRadius, occulting, occultingRadius);
}
/** Build a new eclipse detector.
* <p>The new instance is a total eclipse (umbra) detector.</p>
* <p>The maximal interval between eclipse checks should be smaller than
* the half duration of the minimal pass to handle, otherwise some short
* passes could be missed.</p>
* @param maxCheck maximal checking interval (s)
* @param threshold convergence threshold (s)
* @param occulted the body to be occulted
* @param occultedRadius the radius of the body to be occulted in meters
* @param occulting the occulting body
* @param occultingRadius the occulting body radius in meters
*/
public EclipseDetector(final double maxCheck, final double threshold,
final PVCoordinatesProvider occulted, final double occultedRadius,
final PVCoordinatesProvider occulting, final double occultingRadius) {
this(maxCheck, threshold, DEFAULT_MAX_ITER, new StopOnIncreasing<EclipseDetector>(),
occulted, occultedRadius, occulting, occultingRadius, true);
}
/** 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 occulted the body to be occulted
* @param occultedRadius the radius of the body to be occulted in meters
* @param occulting the occulting body
* @param occultingRadius the occulting body radius in meters
* @param totalEclipse umbra (true) or penumbra (false) detection flag
* @since 6.1
*/
private EclipseDetector(final double maxCheck, final double threshold,
final int maxIter, final EventHandler<? super EclipseDetector> handler,
final PVCoordinatesProvider occulted, final double occultedRadius,
final PVCoordinatesProvider occulting, final double occultingRadius,
final boolean totalEclipse) {
super(maxCheck, threshold, maxIter, handler);
this.occulted = occulted;
this.occultedRadius = FastMath.abs(occultedRadius);
this.occulting = occulting;
this.occultingRadius = FastMath.abs(occultingRadius);
this.totalEclipse = totalEclipse;
}
/** {@inheritDoc} */
@Override
protected EclipseDetector create(final double newMaxCheck, final double newThreshold,
final int nawMaxIter, final EventHandler<? super EclipseDetector> newHandler) {
return new EclipseDetector(newMaxCheck, newThreshold, nawMaxIter, newHandler,
occulted, occultedRadius, occulting, occultingRadius, totalEclipse);
}
/**
* Setup the detector to full umbra detection.
* <p>
* This will override a penumbra/umbra flag if it has been configured previously.
* </p>
* @return a new detector with updated configuration (the instance is not changed)
* @see #withPenumbra()
* @since 6.1
*/
public EclipseDetector withUmbra() {
return new EclipseDetector(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
occulted, occultedRadius, occulting, occultingRadius,
true);
}
/**
* Setup the detector to penumbra detection.
* <p>
* This will override a penumbra/umbra flag if it has been configured previously.
* </p>
* @return a new detector with updated configuration (the instance is not changed)
* @see #withUmbra()
* @since 6.1
*/
public EclipseDetector withPenumbra() {
return new EclipseDetector(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
occulted, occultedRadius, occulting, occultingRadius,
false);
}
/** Get the occulting body.
* @return the occulting body
*/
public PVCoordinatesProvider getOcculting() {
return occulting;
}
/** Get the occulting body radius (m).
* @return the occulting body radius
*/
public double getOccultingRadius() {
return occultingRadius;
}
/** Get the occulted body.
* @return the occulted body
*/
public PVCoordinatesProvider getOcculted() {
return occulted;
}
/** Get the occulted body radius (m).
* @return the occulted body radius
*/
public double getOccultedRadius() {
return occultedRadius;
}
/** Get the total eclipse detection flag.
* @return the total eclipse detection flag (true for umbra events detection,
* false for penumbra events detection)
*/
public boolean getTotalEclipse() {
return totalEclipse;
}
/** Compute the value of the switching function.
* This function becomes negative when entering the region of shadow
* and positive when exiting.
* @param s the current state information: date, kinematics, attitude
* @return value of the switching function
* @exception OrekitException if some specific error occurs
*/
public double g(final SpacecraftState s) throws OrekitException {
final Vector3D pted = occulted.getPVCoordinates(s.getDate(), s.getFrame()).getPosition();
final Vector3D ping = occulting.getPVCoordinates(s.getDate(), s.getFrame()).getPosition();
final Vector3D psat = s.getPVCoordinates().getPosition();
final Vector3D ps = pted.subtract(psat);
final Vector3D po = ping.subtract(psat);
final double angle = Vector3D.angle(ps, po);
final double rs = FastMath.asin(occultedRadius / ps.getNorm());
if (Double.isNaN(rs)) {
return FastMath.PI;
}
final double ro = FastMath.asin(occultingRadius / po.getNorm());
if (Double.isNaN(ro)) {
return -FastMath.PI;
}
return totalEclipse ? (angle - ro + rs) : (angle - ro - rs);
}
}