LnsCoefficients.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.utilities;
import java.util.TreeMap;
import org.orekit.propagation.semianalytical.dsst.utilities.CoefficientsFactory.NSKey;
/** Compute the L<sub>n</sub><sup>s</sup>(γ).
* <p>
* The fomula used is: <br>
* L<sub>n</sub><sup>s</sup>(γ) = ( R / a )<sup>n</sup>V<sub>ns</sub>Q<sup>ns</sup>(γ)
* </p>
* @author Lucian Barbulescu
*/
public class LnsCoefficients {
/** The coefficients L<sub>n</sub><sup>s</sup>(γ). */
private final double[][] lns;
/** The coefficients dL<sub>n</sub><sup>s</sup>(γ) / dγ. */
private final double[][] dlns;
/** Create a set of L<sub>n</sub><sup>s</sup>(γ) coefficients.
*
* @param nMax maximum value for n
* @param sMax maximum value for s
* @param Qns the Q<sup>ns</sup>(γ) coefficients
* @param Vns the V<sub>ns</sub> coefficients
* @param roa (R / a)
*/
public LnsCoefficients(final int nMax, final int sMax,
final double[][] Qns, final TreeMap<NSKey, Double> Vns, final double roa) {
final int rows = nMax + 1;
final int columns = sMax + 1;
this.lns = new double[rows][columns];
this.dlns = new double[rows][columns];
final double[] roaPow = new double[rows];
roaPow[0] = 1.;
for (int i = 1; i <= nMax; i++) {
roaPow[i] = roa * roaPow[i - 1];
}
for (int s = 0; s <= sMax; s++) {
for (int n = s; n <= nMax; n++) {
// if (n - s) is not even L<sub>n</sub><sup>s</sup>(γ) is 0
if ((n - s) % 2 == 0) {
final double coef = roaPow[n] * Vns.get(new NSKey(n, s));
lns[n][s] = coef * Qns[n][s];
if ( n == s) {
// if n == s the derivative is 0 because Q[n][s+1] == Q[n][n+1] is 0
dlns[n][s] = 0;
} else {
dlns[n][s] = coef * Qns[n][s + 1];
}
} else {
lns[n][s] = 0.;
dlns[n][s] = 0;
}
}
}
}
/**Get the value of L<sub>n</sub><sup>s</sup>(γ).
*
* @param n n index
* @param s s index
* @return L<sub>n</sub><sup>s</sup>(γ)
*/
public double getLns(final int n, final int s) {
return lns[n][s];
}
/**Get the value of dL<sub>n</sub><sup>s</sup> / dγ (γ).
*
* @param n n index
* @param s s index
* @return L<sub>n</sub><sup>s</sup>(γ)
*/
public double getdLnsdGamma(final int n, final int s) {
return dlns[n][s];
}
}