/**
* Simple constructor.
*
* <p>The {@code applyBefore} parameter is mainly used when the differential effect is associated
* with a maneuver. In this case, the parameter must be set to {@code false}.
*
* @param orbit0 original orbit at reference date
* @param orbit1 shifted orbit at reference date
* @param applyBefore if true, effect is applied both before and after reference date, if false it
* is only applied after reference date
* @param gravityField gravity field to use
* @exception OrekitException if gravity field does not contain J2 coefficient
*/
public J2DifferentialEffect(
final Orbit orbit0,
final Orbit orbit1,
final boolean applyBefore,
final UnnormalizedSphericalHarmonicsProvider gravityField)
throws OrekitException {
this(
orbit0,
orbit1,
applyBefore,
gravityField.getAe(),
gravityField.getMu(),
-gravityField.onDate(orbit0.getDate()).getUnnormalizedCnm(2, 0));
}
/**
* Simple constructor.
*
* <p>The {@code applyBefore} parameter is mainly used when the differential effect is associated
* with a maneuver. In this case, the parameter must be set to {@code false}.
*
* @param original original state at reference date
* @param directEffect direct effect changing the orbit
* @param applyBefore if true, effect is applied both before and after reference date, if false it
* is only applied after reference date
* @param gravityField gravity field to use
* @exception OrekitException if gravity field does not contain J2 coefficient
*/
public J2DifferentialEffect(
final SpacecraftState original,
final AdapterPropagator.DifferentialEffect directEffect,
final boolean applyBefore,
final UnnormalizedSphericalHarmonicsProvider gravityField)
throws OrekitException {
this(
original,
directEffect,
applyBefore,
gravityField.getAe(),
gravityField.getMu(),
-gravityField.onDate(original.getDate()).getUnnormalizedCnm(2, 0));
}
/** {@inheritDoc} */
@Override
public double[] getShortPeriodicVariations(final AbsoluteDate date, final double[] meanElements)
throws OrekitException {
// Initialise the short periodic variations
final double[] shortPeriodicVariation = new double[] {0., 0., 0., 0., 0., 0.};
// Compute only if there is at least one non-resonant tesseral or
// only the m-daily tesseral should be taken into account
if (!nonResOrders.isEmpty() || mDailiesOnly) {
// Build an Orbit object from the mean elements
final Orbit meanOrbit =
OrbitType.EQUINOCTIAL.mapArrayToOrbit(
meanElements, PositionAngle.MEAN, date, provider.getMu(), this.frame);
// Build an auxiliary object
final AuxiliaryElements aux = new AuxiliaryElements(meanOrbit, I);
// Central body rotation angle from equation 2.7.1-(3)(4).
final Transform t = bodyFrame.getTransformTo(aux.getFrame(), aux.getDate());
final Vector3D xB = t.transformVector(Vector3D.PLUS_I);
final Vector3D yB = t.transformVector(Vector3D.PLUS_J);
final double currentTheta =
FastMath.atan2(
-f.dotProduct(yB) + I * g.dotProduct(xB), f.dotProduct(xB) + I * g.dotProduct(yB));
// Add the m-daily contribution
for (int m = 1; m <= maxOrderMdailyTesseralSP; m++) {
// Phase angle
final double jlMmt = -m * currentTheta;
final double sinPhi = FastMath.sin(jlMmt);
final double cosPhi = FastMath.cos(jlMmt);
// compute contribution for each element
for (int i = 0; i < 6; i++) {
shortPeriodicVariation[i] +=
tesseralSPCoefs.getCijm(i, 0, m, date) * cosPhi
+ tesseralSPCoefs.getSijm(i, 0, m, date) * sinPhi;
}
}
// loop through all non-resonant (j,m) pairs
for (final Map.Entry<Integer, List<Integer>> entry : nonResOrders.entrySet()) {
final int m = entry.getKey();
final List<Integer> listJ = entry.getValue();
for (int j : listJ) {
// Phase angle
final double jlMmt = j * meanElements[5] - m * currentTheta;
final double sinPhi = FastMath.sin(jlMmt);
final double cosPhi = FastMath.cos(jlMmt);
// compute contribution for each element
for (int i = 0; i < 6; i++) {
shortPeriodicVariation[i] +=
tesseralSPCoefs.getCijm(i, j, m, date) * cosPhi
+ tesseralSPCoefs.getSijm(i, j, m, date) * sinPhi;
}
}
}
}
return shortPeriodicVariation;
}
/** {@inheritDoc} */
@Override
public void initializeStep(final AuxiliaryElements aux) throws OrekitException {
// Equinoctial elements
a = aux.getSma();
k = aux.getK();
h = aux.getH();
q = aux.getQ();
p = aux.getP();
lm = aux.getLM();
// Eccentricity
ecc = aux.getEcc();
e2 = ecc * ecc;
// Retrograde factor
I = aux.getRetrogradeFactor();
// Equinoctial frame vectors
f = aux.getVectorF();
g = aux.getVectorG();
// Central body rotation angle from equation 2.7.1-(3)(4).
final Transform t = bodyFrame.getTransformTo(aux.getFrame(), aux.getDate());
final Vector3D xB = t.transformVector(Vector3D.PLUS_I);
final Vector3D yB = t.transformVector(Vector3D.PLUS_J);
theta =
FastMath.atan2(
-f.dotProduct(yB) + I * g.dotProduct(xB), f.dotProduct(xB) + I * g.dotProduct(yB));
// Direction cosines
alpha = aux.getAlpha();
beta = aux.getBeta();
gamma = aux.getGamma();
// Equinoctial coefficients
// A = sqrt(μ * a)
final double A = aux.getA();
// B = sqrt(1 - h² - k²)
final double B = aux.getB();
// C = 1 + p² + q²
final double C = aux.getC();
// Common factors from equinoctial coefficients
// 2 * a / A
ax2oA = 2. * a / A;
// B / A
BoA = B / A;
// 1 / AB
ooAB = 1. / (A * B);
// C / 2AB
Co2AB = C * ooAB / 2.;
// B / (A * (1 + B))
BoABpo = BoA / (1. + B);
// &mu / a
moa = provider.getMu() / a;
// R / a
roa = provider.getAe() / a;
// Χ = 1 / B
chi = 1. / B;
chi2 = chi * chi;
// mean motion n
meanMotion = aux.getMeanMotion();
}
