AbstractRadiationForceModel.java
/* Copyright 2002-2020 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.forces.radiation;
import java.util.stream.Stream;
import org.hipparchus.Field;
import org.hipparchus.RealFieldElement;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.hipparchus.ode.events.Action;
import org.hipparchus.util.FastMath;
import org.hipparchus.util.MathArrays;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitMessages;
import org.orekit.forces.AbstractForceModel;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.AbstractDetector;
import org.orekit.propagation.events.EventDetector;
import org.orekit.propagation.events.FieldAbstractDetector;
import org.orekit.propagation.events.FieldEventDetector;
import org.orekit.propagation.events.handlers.EventHandler;
import org.orekit.propagation.events.handlers.FieldEventHandler;
import org.orekit.utils.Constants;
import org.orekit.utils.ExtendedPVCoordinatesProvider;
/**
* Base class for radiation force models.
* @see SolarRadiationPressure
* @see ECOM2
* @since 10.2
*/
public abstract class AbstractRadiationForceModel extends AbstractForceModel {
/** Margin to force recompute lighting ratio derivatives when we are really inside penumbra. */
private static final double ANGULAR_MARGIN = 1.0e-10;
/** Central body model. */
private final double equatorialRadius;
/** Sun model. */
private final ExtendedPVCoordinatesProvider sun;
/**
* Constructor.
* @param sun Sun model
* @param equatorialRadius spherical shape model (for umbra/penumbra computation)
*/
protected AbstractRadiationForceModel(final ExtendedPVCoordinatesProvider sun, final double equatorialRadius) {
this.sun = sun;
this.equatorialRadius = equatorialRadius;
}
/** {@inheritDoc} */
@Override
public boolean dependsOnPositionOnly() {
return false;
}
/** {@inheritDoc} */
@Override
public Stream<EventDetector> getEventsDetectors() {
return Stream.of(new UmbraDetector(), new PenumbraDetector());
}
/** {@inheritDoc} */
@Override
public <T extends RealFieldElement<T>> Stream<FieldEventDetector<T>> getFieldEventsDetectors(final Field<T> field) {
return Stream.of(new FieldUmbraDetector<>(field), new FieldPenumbraDetector<>(field));
}
/**
* Get the useful angles for eclipse computation.
* @param sunPosition Sun position in the selected frame
* @param position the satellite's position in the selected frame
* @return the 3 angles {(satCentral, satSun), Central body apparent radius, Sun apparent radius}
*/
protected double[] getEclipseAngles(final Vector3D sunPosition, final Vector3D position) {
final double[] angle = new double[3];
final Vector3D satSunVector = sunPosition.subtract(position);
// Sat-Sun / Sat-CentralBody angle
angle[0] = Vector3D.angle(satSunVector, position.negate());
// Central body apparent radius
final double r = position.getNorm();
if (r <= equatorialRadius) {
throw new OrekitException(OrekitMessages.TRAJECTORY_INSIDE_BRILLOUIN_SPHERE, r);
}
angle[1] = FastMath.asin(equatorialRadius / r);
// Sun apparent radius
angle[2] = FastMath.asin(Constants.SUN_RADIUS / satSunVector.getNorm());
return angle;
}
/**
* Get the useful angles for eclipse computation.
* @param sunPosition Sun position in the selected frame
* @param position the satellite's position in the selected frame.
* @param <T> extends RealFieldElement
* @return the 3 angles {(satCentral, satSun), Central body apparent radius, Sun apparent radius}
*/
protected <T extends RealFieldElement<T>> T[] getEclipseAngles(final FieldVector3D<T> sunPosition, final FieldVector3D<T> position) {
final T[] angle = MathArrays.buildArray(position.getX().getField(), 3);
final FieldVector3D<T> mP = position.negate();
final FieldVector3D<T> satSunVector = mP.add(sunPosition);
// Sat-Sun / Sat-CentralBody angle
angle[0] = FieldVector3D.angle(satSunVector, mP);
// Central body apparent radius
final T r = position.getNorm();
if (r.getReal() <= equatorialRadius) {
throw new OrekitException(OrekitMessages.TRAJECTORY_INSIDE_BRILLOUIN_SPHERE, r);
}
angle[1] = r.reciprocal().multiply(equatorialRadius).asin();
// Sun apparent radius
angle[2] = satSunVector.getNorm().reciprocal().multiply(Constants.SUN_RADIUS).asin();
return angle;
}
/** This class defines the umbra entry/exit detector. */
private class UmbraDetector extends AbstractDetector<UmbraDetector> {
/** Build a new instance. */
UmbraDetector() {
super(60.0, 1.0e-3, DEFAULT_MAX_ITER, new EventHandler<UmbraDetector>() {
/** {@inheritDoc} */
public Action eventOccurred(final SpacecraftState s, final UmbraDetector detector,
final boolean increasing) {
return Action.RESET_DERIVATIVES;
}
});
}
/** 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 UmbraDetector(final double maxCheck, final double threshold,
final int maxIter, final EventHandler<? super UmbraDetector> handler) {
super(maxCheck, threshold, maxIter, handler);
}
/** {@inheritDoc} */
@Override
protected UmbraDetector create(final double newMaxCheck, final double newThreshold,
final int newMaxIter, final EventHandler<? super UmbraDetector> newHandler) {
return new UmbraDetector(newMaxCheck, newThreshold, newMaxIter, newHandler);
}
/** The G-function is the difference between the Sun-Sat-Central-Body angle and
* the central body apparent radius.
* @param s the current state information : date, kinematics, attitude
* @return value of the g function
*/
public double g(final SpacecraftState s) {
final double[] angle = getEclipseAngles(sun.getPVCoordinates(s.getDate(), s.getFrame()).getPosition(),
s.getPVCoordinates().getPosition());
return angle[0] - angle[1] + angle[2] - ANGULAR_MARGIN;
}
}
/** This class defines the penumbra entry/exit detector. */
private class PenumbraDetector extends AbstractDetector<PenumbraDetector> {
/** Build a new instance. */
PenumbraDetector() {
super(60.0, 1.0e-3, DEFAULT_MAX_ITER, new EventHandler<PenumbraDetector>() {
/** {@inheritDoc} */
public Action eventOccurred(final SpacecraftState s, final PenumbraDetector detector,
final boolean increasing) {
return Action.RESET_DERIVATIVES;
}
});
}
/** 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 PenumbraDetector(final double maxCheck, final double threshold,
final int maxIter, final EventHandler<? super PenumbraDetector> handler) {
super(maxCheck, threshold, maxIter, handler);
}
/** {@inheritDoc} */
@Override
protected PenumbraDetector create(final double newMaxCheck, final double newThreshold,
final int newMaxIter, final EventHandler<? super PenumbraDetector> newHandler) {
return new PenumbraDetector(newMaxCheck, newThreshold, newMaxIter, newHandler);
}
/** The G-function is the difference between the Sun-Sat-Central-Body angle and
* the sum of the central body and Sun's apparent radius.
* @param s the current state information : date, kinematics, attitude
* @return value of the g function
*/
public double g(final SpacecraftState s) {
final double[] angle = getEclipseAngles(sun.getPVCoordinates(s.getDate(), s.getFrame()).getPosition(),
s.getPVCoordinates().getPosition());
return angle[0] - angle[1] - angle[2] + ANGULAR_MARGIN;
}
}
/** This class defines the umbra entry/exit detector. */
private class FieldUmbraDetector<T extends RealFieldElement<T>>
extends FieldAbstractDetector<FieldUmbraDetector<T>, T> {
/** Build a new instance.
* @param field field to which elements belong
*/
FieldUmbraDetector(final Field<T> field) {
super(field.getZero().add(60.0), field.getZero().add(1.0e-3),
DEFAULT_MAX_ITER, new FieldEventHandler<FieldUmbraDetector<T>, T>() {
/** {@inheritDoc} */
public Action eventOccurred(final FieldSpacecraftState<T> s,
final FieldUmbraDetector<T> detector,
final boolean increasing) {
return Action.RESET_DERIVATIVES;
}
});
}
/** 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
*/
private FieldUmbraDetector(final T maxCheck, final T threshold,
final int maxIter,
final FieldEventHandler<? super FieldUmbraDetector<T>, T> handler) {
super(maxCheck, threshold, maxIter, handler);
}
/** {@inheritDoc} */
@Override
protected FieldUmbraDetector<T> create(final T newMaxCheck, final T newThreshold,
final int newMaxIter,
final FieldEventHandler<? super FieldUmbraDetector<T>, T> newHandler) {
return new FieldUmbraDetector<>(newMaxCheck, newThreshold, newMaxIter, newHandler);
}
/** The G-function is the difference between the Sun-Sat-Central-Body angle and
* the central body apparent radius.
* @param s the current state information : date, kinematics, attitude
* @return value of the g function
*/
public T g(final FieldSpacecraftState<T> s) {
final T[] angle = getEclipseAngles(sun.getPVCoordinates(s.getDate(), s.getFrame()).getPosition(),
s.getPVCoordinates().getPosition());
return angle[0].subtract(angle[1]).add(angle[2]).subtract(ANGULAR_MARGIN);
}
}
/** This class defines the penumbra entry/exit detector. */
private class FieldPenumbraDetector<T extends RealFieldElement<T>>
extends FieldAbstractDetector<FieldPenumbraDetector<T>, T> {
/** Build a new instance.
* @param field field to which elements belong
*/
FieldPenumbraDetector(final Field<T> field) {
super(field.getZero().add(60.0), field.getZero().add(1.0e-3),
DEFAULT_MAX_ITER, new FieldEventHandler<FieldPenumbraDetector<T>, T>() {
/** {@inheritDoc} */
public Action eventOccurred(final FieldSpacecraftState<T> s,
final FieldPenumbraDetector<T> detector,
final boolean increasing) {
return Action.RESET_DERIVATIVES;
}
});
}
/** 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
*/
private FieldPenumbraDetector(final T maxCheck, final T threshold,
final int maxIter,
final FieldEventHandler<? super FieldPenumbraDetector<T>, T> handler) {
super(maxCheck, threshold, maxIter, handler);
}
/** {@inheritDoc} */
@Override
protected FieldPenumbraDetector<T> create(final T newMaxCheck, final T newThreshold,
final int newMaxIter,
final FieldEventHandler<? super FieldPenumbraDetector<T>, T> newHandler) {
return new FieldPenumbraDetector<>(newMaxCheck, newThreshold, newMaxIter, newHandler);
}
/** The G-function is the difference between the Sun-Sat-Central-Body angle and
* the sum of the central body and Sun's apparent radius.
* @param s the current state information : date, kinematics, attitude
* @return value of the g function
*/
public T g(final FieldSpacecraftState<T> s) {
final T[] angle = getEclipseAngles(sun.getPVCoordinates(s.getDate(), s.getFrame()).getPosition(),
s.getPVCoordinates().getPosition());
return angle[0].subtract(angle[1]).subtract(angle[2]).add(ANGULAR_MARGIN);
}
}
}