IsotropicRadiationCNES95Convention.java
/* Copyright 2002-2024 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.ArrayList;
import java.util.Collections;
import java.util.List;
import org.hipparchus.CalculusFieldElement;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.hipparchus.util.FastMath;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.SpacecraftState;
import org.orekit.utils.ParameterDriver;
/** This class represents the features of a simplified spacecraft.
*
* <p>This model uses the coefficients described in the collective
* book edited by CNES in 1995: Spaceflight Dynamics (part I), in
* section 5.2.2.1.3.1 (page 296 of the English edition). The absorption
* coefficient is called α and the specular reflection coefficient is
* called τ. A comment in section 5.2.2.1.3.2 of the same book reads:
* <pre>
* Some authors prefer to express thermo-optical properties for surfaces
* using the following coefficients: Ka = α, Ks = (1-α)τ, Kd = (1-α)(1-τ)
* </pre>
* <p> Ka is the same absorption coefficient, and Ks is also called specular
* reflection coefficient, which leads to a confusion. In fact, as the Ka,
* Ks and Kd coefficients are the most frequently used ones (using the
* names Ca, Cs and Cd), when speaking about reflection coefficients, it
* is more often Cd that is considered rather than τ.
*
* <p>
* The classical set of coefficients Ca, Cs, and Cd are implemented in the
* sister class {@link IsotropicRadiationClassicalConvention}, which should
* probably be preferred to this legacy class.
* </p>
*
* @see org.orekit.forces.BoxAndSolarArraySpacecraft
* @see org.orekit.forces.drag.IsotropicDrag
* @see IsotropicRadiationClassicalConvention
* @author Luc Maisonobe
* @since 7.1
*/
public class IsotropicRadiationCNES95Convention implements RadiationSensitive {
/** Parameters scaling factor.
* <p>
* We use a power of 2 to avoid numeric noise introduction
* in the multiplications/divisions sequences.
* </p>
*/
private final double SCALE = FastMath.scalb(1.0, -3);
/** Drivers for absorption and specular reflection coefficients. */
private final List<ParameterDriver> parameterDrivers;
/** Cross section (m²). */
private final double crossSection;
/** Simple constructor.
* @param crossSection Surface (m²)
* @param alpha absorption coefficient α between 0.0 an 1.0
* @param tau specular reflection coefficient τ between 0.0 an 1.0
*/
public IsotropicRadiationCNES95Convention(final double crossSection, final double alpha, final double tau) {
this.parameterDrivers = new ArrayList<>(3);
parameterDrivers.add(new ParameterDriver(RadiationSensitive.GLOBAL_RADIATION_FACTOR, 1.0, SCALE, 0.0, Double.POSITIVE_INFINITY));
parameterDrivers.add(new ParameterDriver(RadiationSensitive.ABSORPTION_COEFFICIENT, alpha, SCALE, 0.0, 1.0));
parameterDrivers.add(new ParameterDriver(RadiationSensitive.REFLECTION_COEFFICIENT, tau, SCALE, 0.0, 1.0));
this.crossSection = crossSection;
}
/** {@inheritDoc} */
@Override
public List<ParameterDriver> getRadiationParametersDrivers() {
return Collections.unmodifiableList(parameterDrivers);
}
/** {@inheritDoc} */
@Override
public Vector3D radiationPressureAcceleration(final SpacecraftState state, final Vector3D flux,
final double[] parameters) {
final double alpha = parameters[1];
final double tau = parameters[2];
final double kP = parameters[0] * crossSection * (1 + 4 * (1.0 - alpha) * (1.0 - tau) / 9.0);
return new Vector3D(kP / state.getMass(), flux);
}
/** {@inheritDoc} */
@Override
public <T extends CalculusFieldElement<T>> FieldVector3D<T>
radiationPressureAcceleration(final FieldSpacecraftState<T> state,
final FieldVector3D<T> flux,
final T[] parameters) {
final T alpha = parameters[1];
final T tau = parameters[2];
final T kP = alpha.negate().add(1).multiply(tau.negate().add(1)).multiply(4.0 / 9.0).add(1).
multiply(parameters[0]).multiply(crossSection);
return new FieldVector3D<>(state.getMass().reciprocal().multiply(kP), flux);
}
}