LibrationOrbit.java
- /* Copyright 2002-2024 CS GROUP
- * Licensed to CS GROUP (CS) under one or more
- * contributor license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * CS licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- package org.orekit.orbits;
- import org.hipparchus.complex.Complex;
- import org.hipparchus.geometry.euclidean.threed.Vector3D;
- import org.hipparchus.linear.EigenDecompositionNonSymmetric;
- import org.hipparchus.linear.FieldVector;
- import org.hipparchus.linear.MatrixUtils;
- import org.hipparchus.linear.RealMatrix;
- import org.hipparchus.linear.RealVector;
- import org.orekit.bodies.CR3BPSystem;
- import org.orekit.propagation.SpacecraftState;
- import org.orekit.propagation.numerical.cr3bp.STMEquations;
- import org.orekit.utils.PVCoordinates;
- /**
- * Base class for libration orbits.
- * @see HaloOrbit
- * @see LyapunovOrbit
- * @author Vincent Mouraux
- * @author Bryan Cazabonne
- * @since 10.2
- */
- public abstract class LibrationOrbit {
- /** CR3BP System of the libration Orbit. */
- private final CR3BPSystem syst;
- /** Position-Velocity initial position on a libration Orbit. */
- private PVCoordinates initialPV;
- /** Orbital Period of the libration Orbit. */
- private double orbitalPeriod;
- /**
- * Constructor.
- * @param system CR3BP System considered
- * @param initialPV initial position on a libration Orbit
- * @param orbitalPeriod initial orbital period of the libration Orbit
- */
- protected LibrationOrbit(final CR3BPSystem system,
- final PVCoordinates initialPV,
- final double orbitalPeriod) {
- this.syst = system;
- this.initialPV = initialPV;
- this.orbitalPeriod = orbitalPeriod;
- }
- /** Return the orbital period of the libration orbit.
- * @return orbitalPeriod orbital period of the libration orbit
- */
- public double getOrbitalPeriod() {
- return orbitalPeriod;
- }
- /** Return the initialPV on the libration orbit.
- * <p>
- * This will return the exact initialPV only if you applied a prior
- * differential correction. If you did not, you can use the method
- * {@link #applyCorrectionOnPV(CR3BPDifferentialCorrection)}
- * </p>
- * @return initialPV initialPV on the libration orbit
- */
- public PVCoordinates getInitialPV() {
- return initialPV;
- }
- /** Apply differential correction.
- * <p>
- * This will update {@link #initialPV} and
- * {@link #orbitalPeriod} parameters.
- * </p>
- */
- public void applyDifferentialCorrection() {
- final CR3BPDifferentialCorrection diff = new CR3BPDifferentialCorrection(initialPV, syst, orbitalPeriod);
- initialPV = applyCorrectionOnPV(diff);
- orbitalPeriod = diff.getOrbitalPeriod();
- }
- /** Return a manifold direction from one position on a libration Orbit.
- * @param s SpacecraftState with additional equations
- * @param isStable true if the manifold is stable
- * @return manifold first guess Position-Velocity of a point on the libration Orbit
- */
- public PVCoordinates getManifolds(final SpacecraftState s, final boolean isStable) {
- // Get the index of the eigen vector of the state transition matrix,
- // depending on the stability or unstability of the manifold
- final int eigenVectorIndex = isStable ? 1 : 0;
- // Small delta, linked to the characteristic velocity of the CR3BP system
- final double epsilon = syst.getVdim() * 1E2 / syst.getDdim();
- // Get monodromy (i.e. state transition) matrix and its eigen decomposition
- final RealMatrix phi = new STMEquations(syst).getStateTransitionMatrix(s);
- final EigenDecompositionNonSymmetric eigen = new EigenDecompositionNonSymmetric(phi);
- // Get normalized eigen vector linked to the stability of the manifold
- final FieldVector<Complex> cv = eigen.getEigenvector(eigenVectorIndex);
- // Get real vector value and normalize
- final RealVector rv = MatrixUtils.createRealVector(cv.getDimension());
- for (int i = 0; i < cv.getDimension(); ++i) {
- rv.setEntry(i, cv.getEntry(i).getRealPart());
- }
- final RealVector eigenVector = rv.unitVector();
- // New PVCoordinates following the manifold
- return new PVCoordinates(s.getPosition().add(new Vector3D(eigenVector.getEntry(0),
- eigenVector.getEntry(1),
- eigenVector.getEntry(2)).scalarMultiply(epsilon)),
- s.getPVCoordinates().getVelocity().add(new Vector3D(eigenVector.getEntry(3),
- eigenVector.getEntry(4),
- eigenVector.getEntry(5)).scalarMultiply(epsilon)));
- }
- /**
- * Apply the differential correction to compute more accurate initial PV.
- * @param diff cr3bp differential correction
- * @return corrected PV coordinates
- */
- protected abstract PVCoordinates applyCorrectionOnPV(CR3BPDifferentialCorrection diff);
- }