DSSTAtmosphericDrag.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.propagation.semianalytical.dsst.forces;
import org.hipparchus.Field;
import org.hipparchus.RealFieldElement;
import org.hipparchus.util.FastMath;
import org.hipparchus.util.MathArrays;
import org.hipparchus.util.MathUtils;
import org.orekit.forces.drag.DragForce;
import org.orekit.forces.drag.DragSensitive;
import org.orekit.forces.drag.IsotropicDrag;
import org.orekit.models.earth.atmosphere.Atmosphere;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.EventDetector;
import org.orekit.propagation.events.FieldEventDetector;
import org.orekit.propagation.semianalytical.dsst.utilities.AuxiliaryElements;
import org.orekit.propagation.semianalytical.dsst.utilities.FieldAuxiliaryElements;
import org.orekit.utils.Constants;
import org.orekit.utils.ParameterDriver;
/** Atmospheric drag contribution to the
* {@link org.orekit.propagation.semianalytical.dsst.DSSTPropagator DSSTPropagator}.
* <p>
* The drag acceleration is computed through the acceleration model of
* {@link org.orekit.forces.drag.DragForce DragForce}.
* </p>
*
* @author Pascal Parraud
*/
public class DSSTAtmosphericDrag extends AbstractGaussianContribution {
/** Threshold for the choice of the Gauss quadrature order. */
private static final double GAUSS_THRESHOLD = 6.0e-10;
/** Upper limit for atmospheric drag (m) . */
private static final double ATMOSPHERE_ALTITUDE_MAX = 1000000.;
/** Atmospheric drag force model. */
private final DragForce drag;
/** Critical distance from the center of the central body for entering/leaving the atmosphere. */
private final double rbar;
/** Simple constructor with custom force.
* @param force atmospheric drag force model
* @param mu central attraction coefficient
*/
public DSSTAtmosphericDrag(final DragForce force, final double mu) {
//Call to the constructor from superclass using the numerical drag model as ForceModel
super("DSST-drag-", GAUSS_THRESHOLD, force, mu);
this.drag = force;
this.rbar = ATMOSPHERE_ALTITUDE_MAX + Constants.WGS84_EARTH_EQUATORIAL_RADIUS;
}
/** Simple constructor assuming spherical spacecraft.
* @param atmosphere atmospheric model
* @param cd drag coefficient
* @param area cross sectionnal area of satellite
* @param mu central attraction coefficient
*/
public DSSTAtmosphericDrag(final Atmosphere atmosphere, final double cd,
final double area, final double mu) {
this(atmosphere, new IsotropicDrag(area, cd), mu);
}
/** Simple constructor with custom spacecraft.
* @param atmosphere atmospheric model
* @param spacecraft spacecraft model
* @param mu central attraction coefficient
*/
public DSSTAtmosphericDrag(final Atmosphere atmosphere, final DragSensitive spacecraft, final double mu) {
//Call to the constructor from superclass using the numerical drag model as ForceModel
this(new DragForce(atmosphere, spacecraft), mu);
}
/** Get the atmospheric model.
* @return atmosphere model
*/
public Atmosphere getAtmosphere() {
return drag.getAtmosphere();
}
/** Get the critical distance.
* <p>
* The critical distance from the center of the central body aims at
* defining the atmosphere entry/exit.
* </p>
* @return the critical distance from the center of the central body (m)
*/
public double getRbar() {
return rbar;
}
/** {@inheritDoc} */
public EventDetector[] getEventsDetectors() {
return null;
}
/** {@inheritDoc} */
@Override
public <T extends RealFieldElement<T>> FieldEventDetector<T>[] getFieldEventsDetectors(final Field<T> field) {
return null;
}
/** {@inheritDoc} */
protected double[] getLLimits(final SpacecraftState state, final AuxiliaryElements auxiliaryElements) {
final double perigee = auxiliaryElements.getSma() * (1. - auxiliaryElements.getEcc());
// Trajectory entirely out of the atmosphere
if (perigee > rbar) {
return new double[2];
}
final double apogee = auxiliaryElements.getSma() * (1. + auxiliaryElements.getEcc());
// Trajectory entirely within of the atmosphere
if (apogee < rbar) {
return new double[] { -FastMath.PI + MathUtils.normalizeAngle(state.getLv(), 0),
FastMath.PI + MathUtils.normalizeAngle(state.getLv(), 0) };
}
// Else, trajectory partialy within of the atmosphere
final double fb = FastMath.acos(((auxiliaryElements.getSma() * (1. - auxiliaryElements.getEcc() * auxiliaryElements.getEcc()) / rbar) - 1.) / auxiliaryElements.getEcc());
final double wW = FastMath.atan2(auxiliaryElements.getH(), auxiliaryElements.getK());
return new double[] {wW - fb, wW + fb};
}
/** {@inheritDoc} */
protected <T extends RealFieldElement<T>> T[] getLLimits(final FieldSpacecraftState<T> state,
final FieldAuxiliaryElements<T> auxiliaryElements) {
final Field<T> field = state.getDate().getField();
final T zero = field.getZero();
final T[] tab = MathArrays.buildArray(field, 2);
final T perigee = auxiliaryElements.getSma().multiply(auxiliaryElements.getEcc().negate().add(1.));
// Trajectory entirely out of the atmosphere
if (perigee.getReal() > rbar) {
return tab;
}
final T apogee = auxiliaryElements.getSma().multiply(auxiliaryElements.getEcc().add(1.));
// Trajectory entirely within of the atmosphere
if (apogee.getReal() < rbar) {
tab[0] = MathUtils.normalizeAngle(state.getLv(), zero).subtract(FastMath.PI);
tab[1] = MathUtils.normalizeAngle(state.getLv(), zero).add(FastMath.PI);
return tab;
}
// Else, trajectory partialy within of the atmosphere
final T fb = FastMath.acos(((auxiliaryElements.getSma().multiply(auxiliaryElements.getEcc().multiply(auxiliaryElements.getEcc()).negate().add(1.)).divide(rbar)).subtract(1.)).divide(auxiliaryElements.getEcc()));
final T wW = FastMath.atan2(auxiliaryElements.getH(), auxiliaryElements.getK());
tab[0] = wW.subtract(fb);
tab[1] = wW.add(fb);
return tab;
}
/** {@inheritDoc} */
@Override
protected ParameterDriver[] getParametersDriversWithoutMu() {
return drag.getParametersDrivers();
}
/** Get spacecraft shape.
*
* @return spacecraft shape
*/
public DragSensitive getSpacecraft() {
return drag.getSpacecraft();
}
/** Get drag force.
*
* @return drag force
*/
public DragForce getDrag() {
return drag;
}
}