SolarRadiationPressure.java
/* Copyright 2002-2020 CS GROUP
* Licensed to CS GROUP (CS) under one or more
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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
* (the "License"); you may not use this file except in compliance with
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*
* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
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package org.orekit.forces.radiation;
import org.hipparchus.RealFieldElement;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.hipparchus.util.FastMath;
import org.hipparchus.util.Precision;
import org.orekit.frames.Frame;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.SpacecraftState;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.utils.Constants;
import org.orekit.utils.ExtendedPVCoordinatesProvider;
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 AbstractRadiationForceModel {
/** 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;
/** Margin to force recompute lighting ratio derivatives when we are really inside penumbra. */
private static final double ANGULAR_MARGIN = 1.0e-10;
/** Reference flux normalized for a 1m distance (N). */
private final double kRef;
/** Sun model. */
private final ExtendedPVCoordinatesProvider sun;
/** 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
* @since 9.2
*/
public SolarRadiationPressure(final ExtendedPVCoordinatesProvider 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
* @since 9.2
*/
public SolarRadiationPressure(final double dRef, final double pRef,
final ExtendedPVCoordinatesProvider sun,
final double equatorialRadius,
final RadiationSensitive spacecraft) {
super(sun, equatorialRadius);
this.kRef = pRef * dRef * dRef;
this.sun = sun;
this.spacecraft = spacecraft;
}
/** {@inheritDoc} */
@Override
public Vector3D acceleration(final SpacecraftState s, final double[] parameters) {
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 ratio = getLightingRatio(position, frame, date);
final double rawP = ratio * kRef / r2;
final Vector3D flux = new Vector3D(rawP / FastMath.sqrt(r2), sunSatVector);
return spacecraft.radiationPressureAcceleration(date, frame, position, s.getAttitude().getRotation(),
s.getMass(), flux, parameters);
}
/** {@inheritDoc} */
@Override
public <T extends RealFieldElement<T>> FieldVector3D<T> acceleration(final FieldSpacecraftState<T> s,
final T[] parameters) {
final FieldAbsoluteDate<T> date = s.getDate();
final Frame frame = s.getFrame();
final FieldVector3D<T> position = s.getPVCoordinates().getPosition();
final FieldVector3D<T> sunSatVector = position.subtract(sun.getPVCoordinates(date.toAbsoluteDate(), frame).getPosition());
final T r2 = sunSatVector.getNormSq();
// compute flux
final T ratio = getLightingRatio(position, frame, date);
final T rawP = ratio.divide(r2).multiply(kRef);
final FieldVector3D<T> flux = new FieldVector3D<>(rawP.divide(r2.sqrt()), sunSatVector);
return spacecraft.radiationPressureAcceleration(date, frame, position, s.getAttitude().getRotation(),
s.getMass(), flux, parameters);
}
/** 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
* @since 7.1
*/
public double getLightingRatio(final Vector3D position, final Frame frame, final AbsoluteDate date) {
final Vector3D sunPosition = sun.getPVCoordinates(date, frame).getPosition();
if (sunPosition.getNorm() < 2 * Constants.SUN_RADIUS) {
// we are in fact computing a trajectory around Sun (or solar system barycenter),
// not around a planet,we consider lighting ratio is always 1
return 1.0;
}
// Compute useful angles
final double[] angle = getEclipseAngles(sunPosition, position);
// Sat-Sun / Sat-CentralBody angle
final double sunSatCentralBodyAngle = 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 (sunSatCentralBodyAngle - alphaCentral + alphaSun <= ANGULAR_MARGIN) {
result = 0.0;
} else if (sunSatCentralBodyAngle - alphaCentral - alphaSun < -ANGULAR_MARGIN) {
// Compute a lighting ratio in penumbra
final double sEA2 = sunSatCentralBodyAngle * sunSatCentralBodyAngle;
final double oo2sEA = 1.0 / (2. * sunSatCentralBodyAngle);
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 almost0 = Precision.SAFE_MIN;
final double almost1 = FastMath.nextDown(1.0);
final double a1oaS = FastMath.min(almost1, FastMath.max(-almost1, alpha1 / alphaSun));
final double aS2ma12 = FastMath.max(almost0, aS2 - alpha1 * alpha1);
final double a2oaE = FastMath.min(almost1, FastMath.max(-almost1, alpha2 / alphaCentral));
final double aE2ma22 = FastMath.max(almost0, 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;
}
/** 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
* @param <T> extends RealFieldElement
* @return lighting ratio
* @since 7.1
*/
public <T extends RealFieldElement<T>> T getLightingRatio(final FieldVector3D<T> position,
final Frame frame,
final FieldAbsoluteDate<T> date) {
final T one = date.getField().getOne();
final FieldVector3D<T> sunPosition = sun.getPVCoordinates(date, frame).getPosition();
if (sunPosition.getNorm().getReal() < 2 * Constants.SUN_RADIUS) {
// we are in fact computing a trajectory around Sun (or solar system barycenter),
// not around a planet,we consider lighting ratio is always 1
return one;
}
// Compute useful angles
final T[] angle = getEclipseAngles(sunPosition, position);
// Sat-Sun / Sat-CentralBody angle
final T sunsatCentralBodyAngle = angle[0];
// Central Body apparent radius
final T alphaCentral = angle[1];
// Sun apparent radius
final T alphaSun = angle[2];
T result = one;
// Is the satellite in complete umbra ?
if (sunsatCentralBodyAngle.getReal() - alphaCentral.getReal() + alphaSun.getReal() <= ANGULAR_MARGIN) {
result = date.getField().getZero();
} else if (sunsatCentralBodyAngle.getReal() - alphaCentral.getReal() - alphaSun.getReal() < -ANGULAR_MARGIN) {
// Compute a lighting ratio in penumbra
final T sEA2 = sunsatCentralBodyAngle.multiply(sunsatCentralBodyAngle);
final T oo2sEA = sunsatCentralBodyAngle.multiply(2).reciprocal();
final T aS2 = alphaSun.multiply(alphaSun);
final T aE2 = alphaCentral.multiply(alphaCentral);
final T aE2maS2 = aE2.subtract(aS2);
final T alpha1 = sEA2.subtract(aE2maS2).multiply(oo2sEA);
final T alpha2 = sEA2.add(aE2maS2).multiply(oo2sEA);
// Protection against numerical inaccuracy at boundaries
final double almost0 = Precision.SAFE_MIN;
final double almost1 = FastMath.nextDown(1.0);
final T a1oaS = min(almost1, max(-almost1, alpha1.divide(alphaSun)));
final T aS2ma12 = max(almost0, aS2.subtract(alpha1.multiply(alpha1)));
final T a2oaE = min(almost1, max(-almost1, alpha2.divide(alphaCentral)));
final T aE2ma22 = max(almost0, aE2.subtract(alpha2.multiply(alpha2)));
final T P1 = aS2.multiply(a1oaS.acos()).subtract(alpha1.multiply(aS2ma12.sqrt()));
final T P2 = aE2.multiply(a2oaE.acos()).subtract(alpha2.multiply(aE2ma22.sqrt()));
result = one.subtract(P1.add(P2).divide(aS2.multiply(FastMath.PI)));
}
return result;
}
/** {@inheritDoc} */
@Override
public ParameterDriver[] getParametersDrivers() {
return spacecraft.getRadiationParametersDrivers();
}
/** Compute min of two values, one double and one field element.
* @param d double value
* @param f field element
* @param <T> type fo the field elements
* @return min value
*/
private <T extends RealFieldElement<T>> T min(final double d, final T f) {
return (f.getReal() > d) ? f.getField().getZero().add(d) : f;
}
/** Compute max of two values, one double and one field element.
* @param d double value
* @param f field element
* @param <T> type fo the field elements
* @return max value
*/
private <T extends RealFieldElement<T>> T max(final double d, final T f) {
return (f.getReal() <= d) ? f.getField().getZero().add(d) : f;
}
}