1   /* Copyright 2022-2026 Romain Serra
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.control.heuristics;
18  
19  import org.hipparchus.geometry.euclidean.threed.Vector3D;
20  import org.hipparchus.util.FastMath;
21  import org.orekit.orbits.Orbit;
22  import org.orekit.propagation.SpacecraftState;
23  
24  /**
25   * Class modelling impulsive maneuvers to set the osculating semi-major axis to a given value.
26   * The impulse vector is tangential and computed in the same frame as the orbit.
27   * The resulting osculating eccentricity depends on the execution location. The instantaneous orbital plane is left unchanged.
28   * A constraint on the maximum magnitude can be optionally set.
29   * @see AbstractInPlaneImpulseProvider
30   * @author Romain Serra
31   * @since 14.0
32   */
33  public class OsculatingSmaChangeImpulseProvider extends AbstractInPlaneImpulseProvider {
34  
35      /** Target osculating semi-major axis. */
36      private final double targetSemiMajorAxis;
37  
38      /**
39       * Constructor with default maximum magnitude set to positive infinity (unconstrained).
40       * @param targetSemiMajorAxis osculating value to achieve
41       */
42      public OsculatingSmaChangeImpulseProvider(final double targetSemiMajorAxis) {
43          this(Double.POSITIVE_INFINITY, targetSemiMajorAxis);
44      }
45  
46      /**
47       * Constructor.
48       * @param maximumMagnitude maximum magnitude
49       * @param targetSemiMajorAxis osculating value to achieve
50       */
51      public OsculatingSmaChangeImpulseProvider(final double maximumMagnitude, final double targetSemiMajorAxis) {
52          super(maximumMagnitude);
53          this.targetSemiMajorAxis = targetSemiMajorAxis;
54      }
55  
56      @Override
57      public Vector3D getUnconstrainedImpulse(final SpacecraftState state, final boolean isForward) {
58          final Orbit orbit = state.getOrbit();
59          final Vector3D position = orbit.getPosition();
60          final Vector3D velocity = orbit.getVelocity();
61          final double mu = orbit.getMu();
62          final double targetEnergy = -mu / (2. * targetSemiMajorAxis);
63          final double targetSpeed = FastMath.sqrt(2. * (targetEnergy + mu / position.getNorm2()));
64          return velocity.normalize().scalarMultiply(targetSpeed - velocity.getNorm2());
65      }
66  }