DSSTGradientConverter.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.analysis.differentiation.Gradient;
  19. import org.orekit.attitudes.AttitudeProvider;
  20. import org.orekit.attitudes.FieldAttitude;
  21. import org.orekit.orbits.FieldEquinoctialOrbit;
  22. import org.orekit.orbits.FieldOrbit;
  23. import org.orekit.orbits.PositionAngleType;
  24. import org.orekit.propagation.FieldSpacecraftState;
  25. import org.orekit.propagation.SpacecraftState;
  26. import org.orekit.propagation.integration.AbstractGradientConverter;
  27. import org.orekit.time.AbsoluteDate;
  28. import org.orekit.time.FieldAbsoluteDate;

  29. /** Converter for states and parameters arrays.
  30.  * @author Luc Maisonobe
  31.  * @author Bryan Cazabonne
  32.  * @since 10.2
  33.  */
  34. class DSSTGradientConverter extends AbstractGradientConverter {

  35.     /** Fixed dimension of the state. */
  36.     private static final int FREE_STATE_PARAMETERS = 6;

  37.     /** Simple constructor.
  38.      * @param state regular state
  39.      * @param provider provider to use if attitude needs to be recomputed
  40.      */
  41.     DSSTGradientConverter(final SpacecraftState state, final AttitudeProvider provider) {

  42.         super(FREE_STATE_PARAMETERS);

  43.         // equinoctial parameters always has derivatives
  44.         final Gradient sma  = Gradient.variable(FREE_STATE_PARAMETERS, 0, state.getA());
  45.         final Gradient ex   = Gradient.variable(FREE_STATE_PARAMETERS, 1, state.getEquinoctialEx());
  46.         final Gradient ey   = Gradient.variable(FREE_STATE_PARAMETERS, 2, state.getEquinoctialEy());
  47.         final Gradient hx   = Gradient.variable(FREE_STATE_PARAMETERS, 3, state.getHx());
  48.         final Gradient hy   = Gradient.variable(FREE_STATE_PARAMETERS, 4, state.getHy());
  49.         final Gradient l    = Gradient.variable(FREE_STATE_PARAMETERS, 5, state.getLM());

  50.         final Gradient gMu = Gradient.constant(FREE_STATE_PARAMETERS, state.getMu());

  51.         // date
  52.         final AbsoluteDate date = state.getDate();
  53.         final FieldAbsoluteDate<Gradient> dateField = new FieldAbsoluteDate<>(sma.getField(), date);

  54.         // mass never has derivatives
  55.         final Gradient gM = Gradient.constant(FREE_STATE_PARAMETERS, state.getMass());

  56.         final FieldOrbit<Gradient> gOrbit =
  57.                         new FieldEquinoctialOrbit<>(sma, ex, ey, hx, hy, l,
  58.                                                     PositionAngleType.MEAN,
  59.                                                     state.getFrame(),
  60.                                                     dateField,
  61.                                                     gMu);

  62.         final FieldAttitude<Gradient> gAttitude;
  63.         // compute attitude partial derivatives
  64.         gAttitude = provider.getAttitude(gOrbit, gOrbit.getDate(), gOrbit.getFrame());

  65.         // initialize the list with the state having 0 force model parameters
  66.         initStates(new FieldSpacecraftState<>(gOrbit, gAttitude, gM));

  67.     }

  68. }