EclipseDetector.java
- /* Copyright 2002-2022 CS GROUP
- * 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.hipparchus.util.FastMath;
- import org.orekit.bodies.OneAxisEllipsoid;
- 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 occulted body is given through a {@link PVCoordinatesProvider} and its radius in meters. It is modeled as a sphere.
- * </p>
- * <p>Since v10.0 the occulting body is a {@link OneAxisEllipsoid}, before it was modeled as a sphere.
- * <br>It was changed to precisely model Solar eclipses by the Earth, especially for Low Earth Orbits.
- * <br>If you want eclipses by a spherical occulting body, set its flattening to 0. when defining its OneAxisEllipsoid model..
- * </p>
- * <p>The {@link #withUmbra} or {@link #withPenumbra} methods will tell you if the event is triggered when complete umbra/lighting
- * is achieved or when entering/living the penumbra zone.
- * <br>The default behavior is detecting complete umbra/lighting events.
- * <br>If you want to have both, you'll need to set up two distinct detectors.
- * </p>
- * <p>The default implementation behavior is to {@link Action#CONTINUE continue}
- * propagation when entering the eclipse and to {@link Action#STOP stop} propagation
- * when exiting the eclipse.
- * <br>This can be changed by calling {@link #withHandler(EventHandler)} after construction.
- * </p>
- * @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
- * @author Pascal Parraud
- * @author Luc Maisonobe
- */
- public class EclipseDetector extends AbstractDetector<EclipseDetector> {
- /** Occulting body. */
- private final OneAxisEllipsoid occulting;
- /** Occulted body. */
- private final PVCoordinatesProvider occulted;
- /** Occulted body radius (m). */
- private final double occultedRadius;
- /** Umbra, if true, or penumbra, if false, detection flag. */
- private final 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
- * @since 10.0
- */
- public EclipseDetector(final PVCoordinatesProvider occulted, final double occultedRadius,
- final OneAxisEllipsoid occulting) {
- this(DEFAULT_MAXCHECK, DEFAULT_THRESHOLD, DEFAULT_MAX_ITER,
- new StopOnIncreasing<EclipseDetector>(),
- occulted, occultedRadius, occulting, 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 totalEclipse umbra (true) or penumbra (false) detection flag
- * @since 10.0
- */
- private EclipseDetector(final double maxCheck, final double threshold,
- final int maxIter, final EventHandler<? super EclipseDetector> handler,
- final PVCoordinatesProvider occulted, final double occultedRadius,
- final OneAxisEllipsoid occulting, final boolean totalEclipse) {
- super(maxCheck, threshold, maxIter, handler);
- this.occulted = occulted;
- this.occultedRadius = FastMath.abs(occultedRadius);
- this.occulting = occulting;
- 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, 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, 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, false);
- }
- /** Getter for the occulting body.
- * @return the occulting body
- */
- public OneAxisEllipsoid getOcculting() {
- return occulting;
- }
- /** Getter for the occulted body.
- * @return the occulted body
- */
- public PVCoordinatesProvider getOcculted() {
- return occulted;
- }
- /** Getter for the occultedRadius.
- * @return the occultedRadius
- */
- 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
- */
- public double g(final SpacecraftState s) {
- final Vector3D pted = occulted.getPVCoordinates(s.getDate(), occulting.getBodyFrame()).getPosition();
- final Vector3D psat = s.getPVCoordinates(occulting.getBodyFrame()).getPosition();
- final Vector3D plimb = occulting.pointOnLimb(psat, pted);
- final Vector3D ps = psat.subtract(pted);
- final Vector3D pi = psat.subtract(plimb);
- final double angle = Vector3D.angle(ps, psat);
- final double rs = FastMath.asin(occultedRadius / ps.getNorm());
- if (Double.isNaN(rs)) {
- return FastMath.PI;
- }
- final double ro = Vector3D.angle(pi, psat);
- return totalEclipse ? (angle - ro + rs) : (angle - ro - rs);
- }
- }