SolarRadiationPressure.java
/* Copyright 2002-2016 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.forces.radiation;
import org.hipparchus.analysis.differentiation.DerivativeStructure;
import org.hipparchus.geometry.euclidean.threed.FieldRotation;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.hipparchus.util.FastMath;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitMessages;
import org.orekit.forces.AbstractForceModel;
import org.orekit.frames.Frame;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.AbstractDetector;
import org.orekit.propagation.events.EventDetector;
import org.orekit.propagation.events.handlers.EventHandler;
import org.orekit.propagation.numerical.TimeDerivativesEquations;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.Constants;
import org.orekit.utils.PVCoordinatesProvider;
import org.orekit.utils.ParameterDriver;
/** Solar radiation pressure force model.
*
* @author Fabien Maussion
* @author Édouard Delente
* @author Véronique Pommier-Maurussane
* @author Pascal Parraud
*/
public class SolarRadiationPressure extends AbstractForceModel {
/** Reference distance for the solar radiation pressure (m). */
private static final double D_REF = 149597870000.0;
/** Reference solar radiation pressure at D_REF (N/m²). */
private static final double P_REF = 4.56e-6;
/** Reference flux normalized for a 1m distance (N). */
private final double kRef;
/** Sun model. */
private final PVCoordinatesProvider sun;
/** Earth model. */
private final double equatorialRadius;
/** Spacecraft. */
private final RadiationSensitive spacecraft;
/** Simple constructor with default reference values.
* <p>When this constructor is used, the reference values are:</p>
* <ul>
* <li>d<sub>ref</sub> = 149597870000.0 m</li>
* <li>p<sub>ref</sub> = 4.56 10<sup>-6</sup> N/m²</li>
* </ul>
* @param sun Sun model
* @param equatorialRadius spherical shape model (for umbra/penumbra computation)
* @param spacecraft the object physical and geometrical information
*/
public SolarRadiationPressure(final PVCoordinatesProvider sun, final double equatorialRadius,
final RadiationSensitive spacecraft) {
this(D_REF, P_REF, sun, equatorialRadius, spacecraft);
}
/** Complete constructor.
* <p>Note that reference solar radiation pressure <code>pRef</code> in
* N/m² is linked to solar flux SF in W/m² using
* formula pRef = SF/c where c is the speed of light (299792458 m/s). So
* at 1UA a 1367 W/m² solar flux is a 4.56 10<sup>-6</sup>
* N/m² solar radiation pressure.</p>
* @param dRef reference distance for the solar radiation pressure (m)
* @param pRef reference solar radiation pressure at dRef (N/m²)
* @param sun Sun model
* @param equatorialRadius spherical shape model (for umbra/penumbra computation)
* @param spacecraft the object physical and geometrical information
*/
public SolarRadiationPressure(final double dRef, final double pRef,
final PVCoordinatesProvider sun,
final double equatorialRadius,
final RadiationSensitive spacecraft) {
this.kRef = pRef * dRef * dRef;
this.sun = sun;
this.equatorialRadius = equatorialRadius;
this.spacecraft = spacecraft;
}
/** {@inheritDoc} */
public void addContribution(final SpacecraftState s, final TimeDerivativesEquations adder)
throws OrekitException {
final AbsoluteDate date = s.getDate();
final Frame frame = s.getFrame();
final Vector3D position = s.getPVCoordinates().getPosition();
final Vector3D sunSatVector = position.subtract(sun.getPVCoordinates(date, frame).getPosition());
final double r2 = sunSatVector.getNormSq();
// compute flux
final double rawP = kRef * getLightingRatio(position, frame, date) / r2;
final Vector3D flux = new Vector3D(rawP / FastMath.sqrt(r2), sunSatVector);
final Vector3D acceleration = spacecraft.radiationPressureAcceleration(date, frame, position, s.getAttitude().getRotation(),
s.getMass(), flux);
// provide the perturbing acceleration to the derivatives adder
adder.addAcceleration(acceleration, s.getFrame());
}
/** Get the lighting ratio ([0-1]).
* @param position the satellite's position in the selected frame.
* @param frame in which is defined the position
* @param date the date
* @return lighting ratio
* @exception OrekitException if the trajectory is inside the Earth
* @since 7.1
*/
public double getLightingRatio(final Vector3D position, final Frame frame, final AbsoluteDate date)
throws OrekitException {
// Compute useful angles
final double[] angle = getEclipseAngles(position, frame, date);
// Sat-Sun / Sat-CentralBody angle
final double sunEarthAngle = angle[0];
// Central Body apparent radius
final double alphaCentral = angle[1];
// Sun apparent radius
final double alphaSun = angle[2];
double result = 1.0;
// Is the satellite in complete umbra ?
if (sunEarthAngle - alphaCentral + alphaSun <= 0.0) {
result = 0.0;
} else if (sunEarthAngle - alphaCentral - alphaSun < 0.0) {
// Compute a lighting ratio in penumbra
final double sEA2 = sunEarthAngle * sunEarthAngle;
final double oo2sEA = 1.0 / (2. * sunEarthAngle);
final double aS2 = alphaSun * alphaSun;
final double aE2 = alphaCentral * alphaCentral;
final double aE2maS2 = aE2 - aS2;
final double alpha1 = (sEA2 - aE2maS2) * oo2sEA;
final double alpha2 = (sEA2 + aE2maS2) * oo2sEA;
// Protection against numerical inaccuracy at boundaries
final double a1oaS = FastMath.min(1.0, FastMath.max(-1.0, alpha1 / alphaSun));
final double aS2ma12 = FastMath.max(0.0, aS2 - alpha1 * alpha1);
final double a2oaE = FastMath.min(1.0, FastMath.max(-1.0, alpha2 / alphaCentral));
final double aE2ma22 = FastMath.max(0.0, aE2 - alpha2 * alpha2);
final double P1 = aS2 * FastMath.acos(a1oaS) - alpha1 * FastMath.sqrt(aS2ma12);
final double P2 = aE2 * FastMath.acos(a2oaE) - alpha2 * FastMath.sqrt(aE2ma22);
result = 1. - (P1 + P2) / (FastMath.PI * aS2);
}
return result;
}
/** {@inheritDoc} */
public EventDetector[] getEventsDetectors() {
return new EventDetector[] {
new UmbraDetector(), new PenumbraDetector()
};
}
/** {@inheritDoc} */
public ParameterDriver[] getParametersDrivers() {
return spacecraft.getRadiationParametersDrivers();
}
/** {@inheritDoc} */
public FieldVector3D<DerivativeStructure> accelerationDerivatives(final AbsoluteDate date, final Frame frame,
final FieldVector3D<DerivativeStructure> position, final FieldVector3D<DerivativeStructure> velocity,
final FieldRotation<DerivativeStructure> rotation, final DerivativeStructure mass)
throws OrekitException {
final FieldVector3D<DerivativeStructure> sunSatVector = position.subtract(sun.getPVCoordinates(date, frame).getPosition());
final DerivativeStructure r2 = sunSatVector.getNormSq();
// compute flux
final double ratio = getLightingRatio(position.toVector3D(), frame, date);
final DerivativeStructure rawP = r2.reciprocal().multiply(kRef * ratio);
final FieldVector3D<DerivativeStructure> flux = new FieldVector3D<DerivativeStructure>(rawP.divide(r2.sqrt()), sunSatVector);
// compute acceleration with all its partial derivatives
return spacecraft.radiationPressureAcceleration(date, frame, position, rotation, mass, flux);
}
/** {@inheritDoc} */
public FieldVector3D<DerivativeStructure> accelerationDerivatives(final SpacecraftState s, final String paramName)
throws OrekitException {
complainIfNotSupported(paramName);
final AbsoluteDate date = s.getDate();
final Frame frame = s.getFrame();
final Vector3D position = s.getPVCoordinates().getPosition();
final Vector3D sunSatVector = position.subtract(sun.getPVCoordinates(date, frame).getPosition());
final double r2 = sunSatVector.getNormSq();
// compute flux
final double rawP = kRef * getLightingRatio(position, frame, date) / r2;
final Vector3D flux = new Vector3D(rawP / FastMath.sqrt(r2), sunSatVector);
return spacecraft.radiationPressureAcceleration(date, frame, position, s.getAttitude().getRotation(),
s.getMass(), flux, paramName);
}
/** Get the useful angles for eclipse computation.
* @param position the satellite's position in the selected frame.
* @param frame in which is defined the position
* @param date the date
* @return the 3 angles {(satCentral, satSun), Central body apparent radius, Sun apparent radius}
* @exception OrekitException if the trajectory is inside the Earth
*/
private double[] getEclipseAngles(final Vector3D position,
final Frame frame,
final AbsoluteDate date)
throws OrekitException {
final double[] angle = new double[3];
final Vector3D satSunVector = sun.getPVCoordinates(date, frame).getPosition().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;
}
/** This class defines the umbra entry/exit detector. */
private class UmbraDetector extends AbstractDetector<UmbraDetector> {
/** Serializable UID. */
private static final long serialVersionUID = 20141228L;
/** 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 Sat-Sun-Sat-Earth angle and
* the Earth's apparent radius.
* @param s the current state information : date, kinematics, attitude
* @return value of the g function
* @exception OrekitException if sun or spacecraft position cannot be computed
*/
public double g(final SpacecraftState s) throws OrekitException {
final double[] angle = getEclipseAngles(s.getPVCoordinates().getPosition(),
s.getFrame(), s.getDate());
return angle[0] - angle[1] + angle[2];
}
}
/** This class defines the penumbra entry/exit detector. */
private class PenumbraDetector extends AbstractDetector<PenumbraDetector> {
/** Serializable UID. */
private static final long serialVersionUID = 20141228L;
/** 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 Sat-Sun-Sat-Earth angle and
* the sum of the Earth's and Sun's apparent radius.
* @param s the current state information : date, kinematics, attitude
* @return value of the g function
* @exception OrekitException if sun or spacecraft position cannot be computed
*/
public double g(final SpacecraftState s) throws OrekitException {
final double[] angle = getEclipseAngles(s.getPVCoordinates().getPosition(),
s.getFrame(), s.getDate());
return angle[0] - angle[1] - angle[2];
}
}
}