FieldLnsCoefficients.java
/* Copyright 2002-2022 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.utilities;
import java.util.TreeMap;
import org.hipparchus.Field;
import org.hipparchus.CalculusFieldElement;
import org.hipparchus.util.MathArrays;
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 FieldLnsCoefficients <T extends CalculusFieldElement<T>> {
/** The coefficients L<sub>n</sub><sup>s</sup>(γ). */
private final T[][] lns;
/** The coefficients dL<sub>n</sub><sup>s</sup>(γ) / dγ. */
private final T[][] 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)
* @param field field used by default
*/
public FieldLnsCoefficients(final int nMax, final int sMax,
final T[][] Qns, final TreeMap<NSKey, Double> Vns, final T roa,
final Field<T> field) {
final T zero = field.getZero();
final int rows = nMax + 1;
final int columns = sMax + 1;
this.lns = MathArrays.buildArray(field, rows, columns);
this.dlns = MathArrays.buildArray(field, rows, columns);
final T[] roaPow = MathArrays.buildArray(field, rows);
roaPow[0] = zero.add(1.);
for (int i = 1; i <= nMax; i++) {
roaPow[i] = roa.multiply(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 T coef = roaPow[n].multiply(Vns.get(new NSKey(n, s)));
lns[n][s] = coef.multiply(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] = zero;
} else {
dlns[n][s] = coef.multiply(Qns[n][s + 1]);
}
} else {
lns[n][s] = zero;
dlns[n][s] = zero;
}
}
}
}
/**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 T 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 T getdLnsdGamma(final int n, final int s) {
return dlns[n][s];
}
}