DSSTIntegrableJacobianColumnGenerator.java

  1. /* Copyright 2002-2024 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.propagation.semianalytical.dsst;

  18. import org.hipparchus.linear.RealMatrix;
  19. import org.orekit.propagation.SpacecraftState;
  20. import org.orekit.propagation.integration.AdditionalDerivativesProvider;
  21. import org.orekit.propagation.integration.CombinedDerivatives;

  22. /** Generator for one column of a Jacobian matrix.
  23.  * <p>
  24.  * This generator is based on variational equations, so
  25.  * it implements {@link AdditionalDerivativesProvider} and
  26.  * computes only the derivative of the Jacobian column, to
  27.  * be integrated by the propagator alongside the primary state.
  28.  * </p>
  29.  * @author Luc Maisonobe
  30.  * @since 11.1
  31.  */
  32. class DSSTIntegrableJacobianColumnGenerator
  33.     implements AdditionalDerivativesProvider, DSSTStateTransitionMatrixGenerator.DSSTPartialsObserver {

  34.     /** Name of the state for State Transition Matrix. */
  35.     private final String stmName;

  36.     /** Name of the parameter corresponding to the column. */
  37.     private final String columnName;

  38.     /** Last value computed for the partial derivatives. */
  39.     private final double[] pDot;

  40.     /** Simple constructor.
  41.      * <p>
  42.      * The generator for State Transition Matrix <em>must</em> be registered as
  43.      * an integrable generator to the same propagator as the instance, as it
  44.      * must be scheduled to update the state before the instance
  45.      * </p>
  46.      * @param stmGenerator generator for State Transition Matrix
  47.      * @param columnName name of the parameter corresponding to the column
  48.      */
  49.     DSSTIntegrableJacobianColumnGenerator(final DSSTStateTransitionMatrixGenerator stmGenerator, final String columnName) {
  50.         this.stmName    = stmGenerator.getName();
  51.         this.columnName = columnName;
  52.         this.pDot       = new double[getDimension()];
  53.         stmGenerator.addObserver(columnName, this);
  54.     }

  55.     /** {@inheritDoc} */
  56.     @Override
  57.     public String getName() {
  58.         return columnName;
  59.     }

  60.     /** Get the dimension of the generated column.
  61.      * @return dimension of the generated column
  62.      */
  63.     public int getDimension() {
  64.         return 6;
  65.     }

  66.     /** {@inheritDoc}
  67.      * <p>
  68.      * The column derivative can be computed only if the State Transition Matrix derivatives
  69.      * are available, as it implies the STM generator has already been run.
  70.      * </p>
  71.      */
  72.     @Override
  73.     public boolean yields(final SpacecraftState state) {
  74.         return !state.hasAdditionalStateDerivative(stmName);
  75.     }

  76.     /** {@inheritDoc} */
  77.     @Override
  78.     public void partialsComputed(final SpacecraftState state, final RealMatrix factor, final double[] meanElementsPartials) {
  79.         // retrieve current Jacobian column
  80.         final double[] p = state.getAdditionalState(getName());

  81.         // compute time derivative of the Jacobian column
  82.         System.arraycopy(factor.operate(p), 0, pDot, 0, pDot.length);
  83.         for (int i = 0; i < pDot.length; ++i) {
  84.             pDot[i] += meanElementsPartials[i];
  85.         }

  86.     }

  87.     /** {@inheritDoc} */
  88.     @Override
  89.     public CombinedDerivatives combinedDerivatives(final SpacecraftState s) {
  90.         return new CombinedDerivatives(pDot, null);
  91.     }

  92. }