1   /* Copyright 2020-2025 Exotrail
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.conversion.averaging;
18  
19  import org.orekit.forces.gravity.potential.UnnormalizedSphericalHarmonicsProvider;
20  import org.orekit.frames.Frame;
21  import org.orekit.orbits.CircularOrbit;
22  import org.orekit.orbits.Orbit;
23  import org.orekit.orbits.OrbitType;
24  import org.orekit.orbits.PositionAngleType;
25  import org.orekit.propagation.PropagationType;
26  import org.orekit.propagation.analytical.EcksteinHechlerPropagator;
27  import org.orekit.time.AbsoluteDate;
28  import org.orekit.propagation.conversion.averaging.elements.AveragedCircularWithMeanAngle;
29  
30  /**
31   * Class representing an averaged orbital state as in the Eckstein-Hechler theory.
32   *
33   * @author Romain Serra
34   * @see AveragedOrbitalState
35   * @see EcksteinHechlerPropagator
36   * @since 12.1
37   */
38  public class EcksteinHechlerOrbitalState extends AbstractHarmonicsBasedOrbitalState {
39  
40      /** Averaged circular elements. */
41      private final AveragedCircularWithMeanAngle averagedElements;
42  
43      /**
44       * Constructor.
45       * @param date epoch
46       * @param elements averaged orbital elements
47       * @param frame reference frame
48       * @param harmonicsProvider spherical harmonics provider
49       */
50      public EcksteinHechlerOrbitalState(final AbsoluteDate date,
51                                         final AveragedCircularWithMeanAngle elements,
52                                         final Frame frame,
53                                         final UnnormalizedSphericalHarmonicsProvider harmonicsProvider) {
54          super(date, frame, harmonicsProvider);
55          this.averagedElements = elements;
56      }
57  
58      /** {@inheritDoc} */
59      @Override
60      public OrbitType getOrbitType() {
61          return OrbitType.CIRCULAR;
62      }
63  
64      /** {@inheritDoc} */
65      @Override
66      public PositionAngleType getPositionAngleType() {
67          return PositionAngleType.MEAN;
68      }
69  
70      /** {@inheritDoc} */
71      @Override
72      public AveragedCircularWithMeanAngle getAveragedElements() {
73          return averagedElements;
74      }
75  
76      /** {@inheritDoc} */
77      @Override
78      public Orbit toOsculatingOrbit() {
79          final EcksteinHechlerPropagator propagator = createPropagator();
80          return propagator.propagateOrbit(getDate());
81      }
82  
83      /**
84       * Create Eckstein-Hechler propagator.
85       * @return propagator using relevant theory
86       */
87      private EcksteinHechlerPropagator createPropagator() {
88          final CircularOrbit orekitOrbit = createOrekitOrbit();
89          return new EcksteinHechlerPropagator(orekitOrbit, getHarmonicsProvider(),
90                  PropagationType.MEAN);
91      }
92  
93      /**
94       * Create circular orbit representation of averaged state.
95       * @return circular orbit
96       */
97      private CircularOrbit createOrekitOrbit() {
98          return new CircularOrbit(averagedElements.getAveragedSemiMajorAxis(),
99                  averagedElements.getAveragedCircularEx(), averagedElements.getAveragedCircularEy(),
100                 averagedElements.getAveragedInclination(),
101                 averagedElements.getAveragedRightAscensionOfTheAscendingNode(),
102                 averagedElements.getAveragedMeanLatitudeArgument(), getPositionAngleType(),
103                 getFrame(), getDate(), getMu());
104     }
105 
106 }