1   /* Copyright 2002-2025 CS GROUP
2    * Licensed to CS GROUP (CS) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * CS licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *   http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.orekit.forces.gravity.potential;
18  
19  import org.hipparchus.util.SinCos;
20  
21  /** Part of a {@link PiecewiseSphericalHarmonics piecewise gravity fields} valid for one time interval.
22   * @author Luc Maisonobe
23   * @since 11.1
24   */
25  class PiecewisePart {
26  
27      /** Converter between (degree, order) indices and flatten array. */
28      private final Flattener flattener;
29  
30      /** Components of the spherical harmonics. */
31      private final TimeDependentHarmonic[] components;
32  
33      /** Simple constructor.
34       * @param flattener converter between (degree, order) indices and flatten array
35       * @param components components of the spherical harmonics
36       */
37      PiecewisePart(final Flattener flattener, final TimeDependentHarmonic[] components) {
38          this.flattener  = flattener;
39          this.components = components.clone();
40      }
41  
42      /** Get the maximum supported degree.
43       * @return maximal supported degree
44       */
45      public int getMaxDegree() {
46          return flattener.getDegree();
47      }
48  
49      /** Get the maximal supported order.
50       * @return maximal supported order
51       */
52      public int getMaxOrder() {
53          return flattener.getOrder();
54      }
55  
56      /** Compute the time-dependent part of a spherical harmonic cosine coefficient.
57       * @param n degree of the coefficient
58       * @param m order of the coefficient
59       * @param offsets offsets to reference dates in the gravity field
60       * @param pulsations angular pulsations in the gravity field
61       * @return raw coefficient Cnm
62       */
63      public double computeCnm(final int n, final int m,
64                               final double[] offsets, final SinCos[][] pulsations) {
65          final TimeDependentHarmonic harmonic = components[flattener.index(n, m)];
66          return harmonic == null ? 0.0 : harmonic.computeCnm(offsets, pulsations);
67      }
68  
69      /** Compute the time-dependent part of a spherical harmonic sine coefficient.
70       * @param n degree of the coefficient
71       * @param m order of the coefficient
72       * @param offsets offsets to reference dates in the gravity field
73       * @param pulsations angular pulsations in the gravity field
74       * @return raw coefficient Snm
75       */
76      public double computeSnm(final int n, final int m,
77                               final double[] offsets, final SinCos[][] pulsations) {
78          final TimeDependentHarmonic harmonic = components[flattener.index(n, m)];
79          return harmonic == null ? 0.0 : harmonic.computeSnm(offsets, pulsations);
80      }
81  
82  }