DSSTThirdBodyDynamicContext.java
/* Copyright 2002-2023 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.geometry.euclidean.threed.Vector3D;
import org.hipparchus.util.FastMath;
import org.orekit.bodies.CelestialBody;
import org.orekit.propagation.semianalytical.dsst.utilities.AuxiliaryElements;
/**
* This class is a container for the common parameters used in
* {@link DSSTThirdBody}.
* <p>
* It performs parameters initialization at each integration step for the third
* body attraction perturbation. These parameters change for each integration
* step.
* </p>
* @author Bryan Cazabonne
* @since 11.3.3
*/
public class DSSTThirdBodyDynamicContext extends ForceModelContext {
/** Standard gravitational parameter μ for the body in m³/s². */
private double gm;
/** Distance from center of mass of the central body to the 3rd body. */
private double R3;
/** A = sqrt(μ * a). */
private double A;
/** α. */
private double alpha;
/** β. */
private double beta;
/** γ. */
private double gamma;
/** B². */
private double BB;
/** B³. */
private double BBB;
/** Χ = 1 / sqrt(1 - e²) = 1 / B. */
private double X;
/** Χ². */
private double XX;
/** Χ³. */
private double XXX;
/** -2 * a / A. */
private double m2aoA;
/** B / A. */
private double BoA;
/** 1 / (A * B). */
private double ooAB;
/** -C / (2 * A * B). */
private double mCo2AB;
/** B / A(1 + B). */
private double BoABpo;
/** mu3 / R3. */
private double muoR3;
/** b = 1 / (1 + sqrt(1 - e²)) = 1 / (1 + B). */
private double b;
/** h * Χ³. */
private double hXXX;
/** k * Χ³. */
private double kXXX;
/** Keplerian mean motion. */
private double motion;
/** Constructor.
* @param aux auxiliary elements related to the current orbit
* @param body body the 3rd body to consider
* @param parameters values of the force model parameters
*/
public DSSTThirdBodyDynamicContext(final AuxiliaryElements aux,
final CelestialBody body,
final double[] parameters) {
super(aux);
// Parameters related to force model drivers
final double mu = parameters[1];
A = FastMath.sqrt(mu * aux.getSma());
this.gm = parameters[0];
final double absA = FastMath.abs(aux.getSma());
motion = FastMath.sqrt(mu / absA) / absA;
// Distance from center of mass of the central body to the 3rd body
final Vector3D bodyPos = body.getPosition(aux.getDate(), aux.getFrame());
R3 = bodyPos.getNorm();
// Direction cosines
final Vector3D bodyDir = bodyPos.normalize();
alpha = bodyDir.dotProduct(aux.getVectorF());
beta = bodyDir.dotProduct(aux.getVectorG());
gamma = bodyDir.dotProduct(aux.getVectorW());
// Χ<sup>-2</sup>.
BB = aux.getB() * aux.getB();
// Χ<sup>-3</sup>.
BBB = BB * aux.getB();
// b = 1 / (1 + B)
b = 1. / (1. + aux.getB());
// Χ
X = 1. / aux.getB();
XX = X * X;
XXX = X * XX;
// -2 * a / A
m2aoA = -2. * aux.getSma() / A;
// B / A
BoA = aux.getB() / A;
// 1 / AB
ooAB = 1. / (A * aux.getB());
// -C / 2AB
mCo2AB = -aux.getC() * ooAB / 2.;
// B / A(1 + B)
BoABpo = BoA / (1. + aux.getB());
// mu3 / R3
muoR3 = gm / R3;
// h * Χ³
hXXX = aux.getH() * XXX;
// k * Χ³
kXXX = aux.getK() * XXX;
}
/** Get A = sqrt(μ * a).
* @return A
*/
public double getA() {
return A;
}
/** Get the distance from center of mass of the central body to the 3rd body.
* @return the distance from center of mass of the central body to the 3rd body
*/
public double getR3() {
return R3;
}
/** Get direction cosine α for central body.
* @return α
*/
public double getAlpha() {
return alpha;
}
/** Get direction cosine β for central body.
* @return β
*/
public double getBeta() {
return beta;
}
/** Get direction cosine γ for central body.
* @return γ
*/
public double getGamma() {
return gamma;
}
/** Get B².
* @return B²
*/
public double getBB() {
return BB;
}
/** Get B³.
* @return B³
*/
public double getBBB() {
return BBB;
}
/** Get b = 1 / (1 + sqrt(1 - e²)) = 1 / (1 + B).
* @return b
*/
public double getb() {
return b;
}
/** Get Χ = 1 / sqrt(1 - e²) = 1 / B.
* @return Χ
*/
public double getX() {
return X;
}
/** Get Χ².
* @return Χ²
*/
public double getXX() {
return XX;
}
/** Get m2aoA = -2 * a / A.
* @return m2aoA
*/
public double getM2aoA() {
return m2aoA;
}
/** Get B / A.
* @return BoA
*/
public double getBoA() {
return BoA;
}
/** Get ooAB = 1 / (A * B).
* @return ooAB
*/
public double getOoAB() {
return ooAB;
}
/** Get mCo2AB = -C / 2AB.
* @return mCo2AB
*/
public double getMCo2AB() {
return mCo2AB;
}
/** Get BoABpo = B / A(1 + B).
* @return BoABpo
*/
public double getBoABpo() {
return BoABpo;
}
/** Get muoR3 = mu3 / R3.
* @return muoR3
*/
public double getMuoR3() {
return muoR3;
}
/** Get hXXX = h * Χ³.
* @return hXXX
*/
public double getHXXX() {
return hXXX;
}
/** Get kXXX = h * Χ³.
* @return kXXX
*/
public double getKXXX() {
return kXXX;
}
/** Get the Keplerian mean motion.
* <p>The Keplerian mean motion is computed directly from semi major axis
* and central acceleration constant.</p>
* @return Keplerian mean motion in radians per second
*/
public double getMeanMotion() {
return motion;
}
}