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
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17  package org.orekit.models.earth.atmosphere;
18  
19  import org.hipparchus.CalculusFieldElement;
20  import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
21  import org.hipparchus.geometry.euclidean.threed.Vector3D;
22  import org.orekit.frames.FieldKinematicTransform;
23  import org.orekit.frames.Frame;
24  import org.orekit.frames.KinematicTransform;
25  import org.orekit.time.AbsoluteDate;
26  import org.orekit.time.FieldAbsoluteDate;
27  import org.orekit.utils.FieldPVCoordinates;
28  import org.orekit.utils.PVCoordinates;
29  
30  
31  /** Interface for atmospheric models.
32   * @author Luc Maisonobe
33   */
34  public interface Atmosphere {
35  
36      /** Get the frame of the central body.
37       * @return frame of the central body.
38       * @since 6.0
39       */
40      Frame getFrame();
41  
42      /** Get the local density.
43       * @param date current date
44       * @param position current position in frame
45       * @param frame the frame in which is defined the position
46       * @return local density (kg/m³)
47       */
48      double getDensity(AbsoluteDate date, Vector3D position, Frame frame);
49  
50      /** Get the local density.
51       * @param date current date
52       * @param position current position in frame
53       * @param frame the frame in which is defined the position
54       * @param <T> instance of CalculusFieldElement
55       * @return local density (kg/m³)
56       */
57      <T extends CalculusFieldElement<T>> T getDensity(FieldAbsoluteDate<T> date, FieldVector3D<T> position, Frame frame);
58  
59      /** Get the inertial velocity of atmosphere molecules.
60       * <p>By default, atmosphere is supposed to have a null
61       * velocity in the central body frame.</p>
62       *
63       * @param date current date
64       * @param position current position in frame
65       * @param frame the frame in which is defined the position
66       * @return velocity (m/s) (defined in the same frame as the position)
67       */
68      default Vector3D getVelocity(AbsoluteDate date, Vector3D position, Frame frame) {
69          final KinematicTransform bodyToFrame = getFrame().getKinematicTransformTo(frame, date);
70          final Vector3D      posInBody   = bodyToFrame.getStaticInverse().transformPosition(position);
71          final PVCoordinates pvBody      = new PVCoordinates(posInBody, Vector3D.ZERO);
72          final PVCoordinates pvFrame     = bodyToFrame.transformOnlyPV(pvBody);
73          return pvFrame.getVelocity();
74      }
75  
76      /** Get the inertial velocity of atmosphere molecules.
77       * @param date current date
78       * @param position current position in frame
79       * @param frame the frame in which is defined the position
80       * @param <T> instance of CalculusFieldElement
81       * @return velocity (m/s) (defined in the same frame as the position)
82       */
83      default <T extends CalculusFieldElement<T>> FieldVector3D<T> getVelocity(FieldAbsoluteDate<T> date,
84                                                                               FieldVector3D<T> position,
85                                                                               Frame frame) {
86          final FieldKinematicTransform<T> bodyToFrame = getFrame().getKinematicTransformTo(frame, date);
87          final FieldVector3D<T>      posInBody   = bodyToFrame.getStaticInverse().transformPosition(position);
88          final FieldPVCoordinates<T> pvBody      = new FieldPVCoordinates<>(posInBody,
89                  FieldVector3D.getZero(date.getField()));
90          final FieldPVCoordinates<T> pvFrame     = bodyToFrame.transformOnlyPV(pvBody);
91          return pvFrame.getVelocity();
92      }
93  
94  }