FieldDSSTThirdBodyDynamicContext.java
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*
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* Unless required by applicable law or agreed to in writing, software
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package org.orekit.propagation.semianalytical.dsst.forces;
import org.hipparchus.CalculusFieldElement;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.util.FastMath;
import org.orekit.bodies.CelestialBody;
import org.orekit.propagation.semianalytical.dsst.utilities.FieldAuxiliaryElements;
/**
* This class is a container for the common "field" 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 12.0
* @param <T> type of the field elements
*/
public class FieldDSSTThirdBodyDynamicContext<T extends CalculusFieldElement<T>> extends FieldForceModelContext<T> {
/** Standard gravitational parameter μ for the body in m³/s². */
private T gm;
/** Distance from center of mass of the central body to the 3rd body. */
private T R3;
/** A = sqrt(μ * a). */
private T A;
/** α. */
private T alpha;
/** β. */
private T beta;
/** γ. */
private T gamma;
/** B². */
private T BB;
/** B³. */
private T BBB;
/** Χ = 1 / sqrt(1 - e²) = 1 / B. */
private T X;
/** Χ². */
private T XX;
/** Χ³. */
private T XXX;
/** -2 * a / A. */
private T m2aoA;
/** B / A. */
private T BoA;
/** 1 / (A * B). */
private T ooAB;
/** -C / (2 * A * B). */
private T mCo2AB;
/** B / A(1 + B). */
private T BoABpo;
/** mu3 / R3. */
private T muoR3;
/** b = 1 / (1 + sqrt(1 - e²)) = 1 / (1 + B).*/
private T b;
/** h * Χ³. */
private T hXXX;
/** k * Χ³. */
private T kXXX;
/** Keplerian mean motion. */
private T 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 FieldDSSTThirdBodyDynamicContext(final FieldAuxiliaryElements<T> aux,
final CelestialBody body,
final T[] parameters) {
super(aux);
// Parameters related to force model drivers
final T mu = parameters[1];
A = FastMath.sqrt(mu.multiply(aux.getSma()));
this.gm = parameters[0];
final T absA = FastMath.abs(aux.getSma());
motion = FastMath.sqrt(mu.divide(absA)).divide(absA);
// Distance from center of mass of the central body to the 3rd body
final FieldVector3D<T> bodyPos = body.getPVCoordinates(aux.getDate(), aux.getFrame()).getPosition();
R3 = bodyPos.getNorm();
// Direction cosines
final FieldVector3D<T> 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().multiply(aux.getB());
// Χ<sup>-3</sup>.
BBB = BB.multiply(aux.getB());
// b = 1 / (1 + B)
b = aux.getB().add(1.).reciprocal();
// Χ
X = aux.getB().reciprocal();
XX = X.multiply(X);
XXX = X.multiply(XX);
// -2 * a / A
m2aoA = aux.getSma().multiply(-2.).divide(A);
// B / A
BoA = aux.getB().divide(A);
// 1 / AB
ooAB = (A.multiply(aux.getB())).reciprocal();
// -C / 2AB
mCo2AB = aux.getC().multiply(ooAB).divide(2.).negate();
// B / A(1 + B)
BoABpo = BoA.divide(aux.getB().add(1.));
// mu3 / R3
muoR3 = R3.divide(gm).reciprocal();
// h * Χ³
hXXX = XXX.multiply(aux.getH());
// k * Χ³
kXXX = XXX.multiply(aux.getK());
}
/** Get A = sqrt(μ * a).
* @return A
*/
public T 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 T getR3() {
return R3;
}
/** Get direction cosine α for central body.
* @return α
*/
public T getAlpha() {
return alpha;
}
/** Get direction cosine β for central body.
* @return β
*/
public T getBeta() {
return beta;
}
/** Get direction cosine γ for central body.
* @return γ
*/
public T getGamma() {
return gamma;
}
/** Get B².
* @return B²
*/
public T getBB() {
return BB;
}
/** Get B³.
* @return B³
*/
public T getBBB() {
return BBB;
}
/** Get b = 1 / (1 + sqrt(1 - e²)) = 1 / (1 + B).
* @return b
*/
public T getb() {
return b;
}
/** Get Χ = 1 / sqrt(1 - e²) = 1 / B.
* @return Χ
*/
public T getX() {
return X;
}
/** Get Χ².
* @return Χ²
*/
public T getXX() {
return XX;
}
/** Get m2aoA = -2 * a / A.
* @return m2aoA
*/
public T getM2aoA() {
return m2aoA;
}
/** Get B / A.
* @return BoA
*/
public T getBoA() {
return BoA;
}
/** Get ooAB = 1 / (A * B).
* @return ooAB
*/
public T getOoAB() {
return ooAB;
}
/** Get mCo2AB = -C / 2AB.
* @return mCo2AB
*/
public T getMCo2AB() {
return mCo2AB;
}
/** Get BoABpo = B / A(1 + B).
* @return BoABpo
*/
public T getBoABpo() {
return BoABpo;
}
/** Get muoR3 = mu3 / R3.
* @return muoR3
*/
public T getMuoR3() {
return muoR3;
}
/** Get hXXX = h * Χ³.
* @return hXXX
*/
public T getHXXX() {
return hXXX;
}
/** Get kXXX = h * Χ³.
* @return kXXX
*/
public T 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 T getMeanMotion() {
return motion;
}
}