1   /* Copyright 2002-2021 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.propagation.semianalytical.dsst.forces;
18  
19  import org.hipparchus.util.FastMath;
20  import org.orekit.propagation.semianalytical.dsst.utilities.AuxiliaryElements;
21  
22  /**
23   * This class is a container for the common parameters used in {@link AbstractGaussianContribution}.
24   * <p>
25   * It performs parameters initialization at each integration step for the Gaussian contributions
26   * </p>
27   * @author Bryan Cazabonne
28   * @since 10.0
29   */
30  public class AbstractGaussianContributionContext extends ForceModelContext {
31  
32      // CHECKSTYLE: stop VisibilityModifier check
33  
34      /** 2 / (n² * a) . */
35      protected double ton2a;
36  
37      /** 1 / A . */
38      protected double ooA;
39  
40      /** 1 / (A * B) . */
41      protected double ooAB;
42  
43      /** C / (2 * A * B) . */
44      protected double co2AB;
45  
46      /** 1 / (1 + B) . */
47      protected double ooBpo;
48  
49      /** 1 / μ . */
50      protected double ooMu;
51  
52      /** A = sqrt(μ * a). */
53      private final double A;
54  
55      /** Keplerian mean motion. */
56      private final double n;
57  
58      /** Central attraction coefficient. */
59      private double mu;
60  
61      // CHECKSTYLE: resume VisibilityModifier check
62  
63      /**
64       * Simple constructor.
65       *
66       * @param auxiliaryElements auxiliary elements related to the current orbit
67       * @param parameters        parameters values of the force model parameters
68       */
69      AbstractGaussianContributionContext(final AuxiliaryElements auxiliaryElements, final double[] parameters) {
70  
71          super(auxiliaryElements);
72  
73          // mu driver corresponds to the last term of parameters driver array
74          mu = parameters[parameters.length - 1];
75  
76          // Keplerian Mean Motion
77          final double absA = FastMath.abs(auxiliaryElements.getSma());
78          n = FastMath.sqrt(mu / absA) / absA;
79  
80          // sqrt(μ * a)
81          A = FastMath.sqrt(mu * auxiliaryElements.getSma());
82          // 1 / A
83          ooA = 1. / A;
84          // 1 / AB
85          ooAB = ooA / auxiliaryElements.getB();
86          // C / 2AB
87          co2AB = auxiliaryElements.getC() * ooAB / 2.;
88          // 1 / (1 + B)
89          ooBpo = 1. / (1. + auxiliaryElements.getB());
90          // 2 / (n² * a)
91          ton2a = 2. / (n * n * auxiliaryElements.getSma());
92          // 1 / mu
93          ooMu = 1. / mu;
94  
95      }
96  
97      /** Get central attraction coefficient.
98       * @return mu
99       */
100     public double getMu() {
101         return mu;
102     }
103 
104     /** Get ooA = 1 / A.
105      * @return ooA
106      */
107     public double getOOA() {
108         return ooA;
109     }
110 
111     /** Get ooAB = 1 / (A * B).
112      * @return ooAB
113      */
114     public double getOOAB() {
115         return ooAB;
116     }
117 
118     /** Get co2AB = C / 2AB.
119      * @return co2AB
120      */
121     public double getCo2AB() {
122         return co2AB;
123     }
124 
125     /** Get ooBpo = 1 / (B + 1).
126      * @return ooBpo
127      */
128     public double getOoBpo() {
129         return ooBpo;
130     }
131 
132     /** Get ton2a = 2 / (n² * a).
133      * @return ton2a
134      */
135     public double getTon2a() {
136         return ton2a;
137     }
138 
139     /** Get ooMu = 1 / mu.
140      * @return ooMu
141      */
142     public double getOoMU() {
143         return ooMu;
144     }
145 
146     /** Get the Keplerian mean motion.
147      * <p>The Keplerian mean motion is computed directly from semi major axis
148      * and central acceleration constant.</p>
149      * @return Keplerian mean motion in radians per second
150      */
151     public double getMeanMotion() {
152         return n;
153     }
154 }