DSSTZonalContext.java
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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
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package org.orekit.propagation.semianalytical.dsst.forces;
import org.hipparchus.util.FastMath;
import org.orekit.forces.gravity.potential.UnnormalizedSphericalHarmonicsProvider;
import org.orekit.propagation.semianalytical.dsst.utilities.AuxiliaryElements;
/**
* This class is a container for the common parameters used in {@link DSSTZonal}.
* <p>
* It performs parameters initialization at each integration step for the Zonal contribution
* to the central body gravitational perturbation.
* <p>
* @author Bryan Cazabonne
* @since 10.0
*/
public class DSSTZonalContext extends ForceModelContext {
// Common factors for potential computation
/** A = sqrt(μ * a). */
private final double A;
/** Χ = 1 / sqrt(1 - e²) = 1 / B. */
private double X;
/** Χ². */
private double XX;
/** Χ³. */
private double XXX;
/** 1 / (A * B) . */
private double ooAB;
/** B / A . */
private double BoA;
/** B / A(1 + B) . */
private double BoABpo;
/** -C / (2 * A * B) . */
private double mCo2AB;
/** -2 * a / A . */
private double m2aoA;
/** μ / a . */
private double muoa;
/** R / a . */
private double roa;
/** Keplerian mean motion. */
private final double n;
// Short period terms
/** h * k. */
private double hk;
/** k² - h². */
private double k2mh2;
/** (k² - h²) / 2. */
private double k2mh2o2;
/** 1 / (n² * a²). */
private double oon2a2;
/** 1 / (n² * a) . */
private double oon2a;
/** χ³ / (n² * a). */
private double x3on2a;
/** χ / (n² * a²). */
private double xon2a2;
/** (C * χ) / ( 2 * n² * a² ). */
private double cxo2n2a2;
/** (χ²) / (n² * a² * (χ + 1 ) ). */
private double x2on2a2xp1;
/** B * B. */
private double BB;
/**
* Simple constructor.
*
* @param auxiliaryElements auxiliary elements related to the current orbit
* @param provider provider for spherical harmonics
* @param parameters values of the force model parameters
*/
DSSTZonalContext(final AuxiliaryElements auxiliaryElements,
final UnnormalizedSphericalHarmonicsProvider provider,
final double[] parameters) {
super(auxiliaryElements);
final double mu = parameters[0];
// Keplerian Mean Motion
final double absA = FastMath.abs(auxiliaryElements.getSma());
n = FastMath.sqrt(mu / absA) / absA;
A = FastMath.sqrt(mu * auxiliaryElements.getSma());
// Χ = 1 / B
X = 1. / auxiliaryElements.getB();
XX = X * X;
XXX = X * XX;
// 1 / AB
ooAB = 1. / (A * auxiliaryElements.getB());
// B / A
BoA = auxiliaryElements.getB() / A;
// -C / 2AB
mCo2AB = -auxiliaryElements.getC() * ooAB / 2.;
// B / A(1 + B)
BoABpo = BoA / (1. + auxiliaryElements.getB());
// -2 * a / A
m2aoA = -2 * auxiliaryElements.getSma() / A;
// μ / a
muoa = mu / auxiliaryElements.getSma();
// R / a
roa = provider.getAe() / auxiliaryElements.getSma();
// Short period terms
// h * k.
hk = auxiliaryElements.getH() * auxiliaryElements.getK();
// k² - h².
k2mh2 = auxiliaryElements.getK() * auxiliaryElements.getK() - auxiliaryElements.getH() * auxiliaryElements.getH();
// (k² - h²) / 2.
k2mh2o2 = k2mh2 / 2.;
// 1 / (n² * a²) = 1 / (n * A)
oon2a2 = 1 / (A * n);
// 1 / (n² * a) = a / (n * A)
oon2a = auxiliaryElements.getSma() * oon2a2;
// χ³ / (n² * a)
x3on2a = XXX * oon2a;
// χ / (n² * a²)
xon2a2 = X * oon2a2;
// (C * χ) / ( 2 * n² * a² )
cxo2n2a2 = xon2a2 * auxiliaryElements.getC() / 2;
// (χ²) / (n² * a² * (χ + 1 ) )
x2on2a2xp1 = xon2a2 * X / (X + 1);
// B * B
BB = auxiliaryElements.getB() * auxiliaryElements.getB();
}
/** 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 Χ³.
* @return Χ³
*/
public double getXXX() {
return XXX;
}
/** 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 μ / a .
* @return muoa
*/
public double getMuoa() {
return muoa;
}
/** Get roa = R / a.
* @return roa
*/
public double getRoa() {
return roa;
}
/** 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 n;
}
/** Get h * k.
* @return hk
*/
public double getHK() {
return hk;
}
/** Get k² - h².
* @return k2mh2
*/
public double getK2MH2() {
return k2mh2;
}
/** Get (k² - h²) / 2.
* @return k2mh2o2
*/
public double getK2MH2O2() {
return k2mh2o2;
}
/** Get 1 / (n² * a²).
* @return oon2a2
*/
public double getOON2A2() {
return oon2a2;
}
/** Get χ³ / (n² * a).
* @return x3on2a
*/
public double getX3ON2A() {
return x3on2a;
}
/** Get χ / (n² * a²).
* @return xon2a2
*/
public double getXON2A2() {
return xon2a2;
}
/** Get (C * χ) / ( 2 * n² * a² ).
* @return cxo2n2a2
*/
public double getCXO2N2A2() {
return cxo2n2a2;
}
/** Get (χ²) / (n² * a² * (χ + 1 ) ).
* @return x2on2a2xp1
*/
public double getX2ON2A2XP1() {
return x2on2a2xp1;
}
/** Get B * B.
* @return BB
*/
public double getBB() {
return BB;
}
}