1   /* Copyright 2002-2020 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.attitudes;
18  
19  import org.hipparchus.RealFieldElement;
20  import org.hipparchus.geometry.euclidean.threed.Rotation;
21  import org.orekit.annotation.DefaultDataContext;
22  import org.orekit.data.DataContext;
23  import org.orekit.frames.FieldTransform;
24  import org.orekit.frames.Frame;
25  import org.orekit.frames.Transform;
26  import org.orekit.time.AbsoluteDate;
27  import org.orekit.time.FieldAbsoluteDate;
28  import org.orekit.utils.FieldPVCoordinatesProvider;
29  import org.orekit.utils.PVCoordinatesProvider;
30  
31  
32  /**
33   * This class handles an inertial attitude provider.
34   * <p>Instances of this class are guaranteed to be immutable.</p>
35   * @author Luc Maisonobe
36   */
37  public class InertialProvider implements AttitudeProvider {
38  
39  
40      /** Dummy attitude provider, perfectly aligned with the EME2000 frame.
41       *
42       * <p>This field uses the {@link DataContext#getDefault() default data context}.
43       *
44       * @see #InertialProvider(Rotation, Frame)
45       * @see #InertialProvider(Frame)
46       */
47      @DefaultDataContext
48      public static final InertialProvider EME2000_ALIGNED =
49          new InertialProvider(Rotation.IDENTITY);
50  
51      /** Fixed satellite frame. */
52      private final Frame satelliteFrame;
53  
54      /** Creates new instance.
55       *
56       * <p>This constructor uses the {@link DataContext#getDefault() default data context}.
57       *
58       * @param rotation rotation from EME2000 to the desired satellite frame
59       * @see #InertialProvider(Rotation, Frame)
60       */
61      @DefaultDataContext
62      public InertialProvider(final Rotation rotation) {
63          this(rotation, DataContext.getDefault().getFrames().getEME2000());
64      }
65  
66      /**
67       * Creates new instance aligned with the given frame.
68       *
69       * @param frame the reference frame for the attitude.
70       */
71      public InertialProvider(final Frame frame) {
72          this(Rotation.IDENTITY, frame);
73      }
74  
75      /**
76       * Creates new instance with a fixed attitude in the given frame.
77       *
78       * @param rotation  rotation from {@code reference} to the desired satellite frame
79       * @param reference frame for {@code rotation}.
80       * @since 10.1
81       */
82      public InertialProvider(final Rotation rotation,
83                              final Frame reference) {
84          satelliteFrame =
85              new Frame(reference,
86                      new Transform(AbsoluteDate.ARBITRARY_EPOCH, rotation), null, false);
87      }
88  
89      /** {@inheritDoc} */
90      public Attitude getAttitude(final PVCoordinatesProvider pvProv,
91                                  final AbsoluteDate date, final Frame frame) {
92          final Transform t = frame.getTransformTo(satelliteFrame, date);
93          return new Attitude(date, frame, t.getRotation(), t.getRotationRate(), t.getRotationAcceleration());
94      }
95  
96      /** {@inheritDoc} */
97      public <T extends RealFieldElement<T>>FieldAttitude<T> getAttitude(final FieldPVCoordinatesProvider<T> pvProv,
98                                                                         final FieldAbsoluteDate<T> date, final Frame frame) {
99          final FieldTransform<T> t = frame.getTransformTo(satelliteFrame, date);
100         return new FieldAttitude<>(date, frame, t.getRotation(), t.getRotationRate(), t.getRotationAcceleration());
101     }
102 
103 }