TroposphericDSConverter.java

  1. /* Copyright 2002-2019 CS Systèmes d'Information
  2.  * Licensed to CS Systèmes d'Information (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.estimation.measurements.modifiers;

  19. import java.util.ArrayList;
  20. import java.util.List;

  22. import org.hipparchus.analysis.differentiation.DSFactory;
  23. import org.hipparchus.analysis.differentiation.DerivativeStructure;
  24. import org.hipparchus.geometry.euclidean.threed.FieldRotation;
  25. import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
  26. import org.hipparchus.geometry.euclidean.threed.Vector3D;
  27. import org.orekit.attitudes.AttitudeProvider;
  28. import org.orekit.attitudes.FieldAttitude;
  29. import org.orekit.models.earth.DiscreteTroposphericModel;
  30. import org.orekit.orbits.FieldCartesianOrbit;
  31. import org.orekit.orbits.FieldOrbit;
  32. import org.orekit.propagation.FieldSpacecraftState;
  33. import org.orekit.propagation.SpacecraftState;
  34. import org.orekit.utils.FieldAngularCoordinates;
  35. import org.orekit.utils.FieldPVCoordinates;
  36. import org.orekit.utils.ParameterDriver;
  37. import org.orekit.utils.TimeStampedFieldAngularCoordinates;
  38. import org.orekit.utils.TimeStampedFieldPVCoordinates;

  40. /** Converter for states and parameters arrays.
  41.  * @author Luc Maisonobe
  42.  */
  43. public class TroposphericDSConverter {

  45.     /** Dimension of the state. */
  46.     private final int freeStateParameters;

  48.     /** States with various number of additional parameters for tropospheric models. */
  49.     private final List<FieldSpacecraftState<DerivativeStructure>> dsStates;

  51.     /** Simple constructor.
  52.      * @param state regular state
  53.      * @param freeStateParameters number of free parameters, either 3 (position) or 6 (position-velocity)
  54.      * @param provider provider to use if attitude needs to be recomputed
  55.      */
  56.     public TroposphericDSConverter(final SpacecraftState state, final int freeStateParameters, final AttitudeProvider provider) {

  58.         this.freeStateParameters = freeStateParameters;

  60.         // prepare derivation variables, position, optionally velocity
  61.         final DSFactory factory = new DSFactory(freeStateParameters, 1);

  63.         // position always has derivatives
  64.         final Vector3D pos = state.getPVCoordinates().getPosition();
  65.         final FieldVector3D<DerivativeStructure> posDS = new FieldVector3D<>(factory.variable(0, pos.getX()),
  66.                                                                              factory.variable(1, pos.getY()),
  67.                                                                              factory.variable(2, pos.getZ()));

  69.         // velocity may have derivatives or not
  70.         final Vector3D vel = state.getPVCoordinates().getVelocity();
  71.         final FieldVector3D<DerivativeStructure> velDS;
  72.         if (freeStateParameters > 3) {
  73.             velDS = new FieldVector3D<>(factory.variable(3, vel.getX()),
  74.                                         factory.variable(4, vel.getY()),
  75.                                         factory.variable(5, vel.getZ()));
  76.         } else {
  77.             velDS = new FieldVector3D<>(factory.constant(vel.getX()),
  78.                                         factory.constant(vel.getY()),
  79.                                         factory.constant(vel.getZ()));
  80.         }

  82.         // acceleration never has derivatives
  83.         final Vector3D acc = state.getPVCoordinates().getAcceleration();
  84.         final FieldVector3D<DerivativeStructure> accDS = new FieldVector3D<>(factory.constant(acc.getX()),
  85.                                                                              factory.constant(acc.getY()),
  86.                                                                              factory.constant(acc.getZ()));

  88.         // mass never has derivatives
  89.         final DerivativeStructure dsM = factory.constant(state.getMass());

  91.         final FieldOrbit<DerivativeStructure> dsOrbit =
  92.                         new FieldCartesianOrbit<>(new TimeStampedFieldPVCoordinates<>(state.getDate(), posDS, velDS, accDS),
  93.                                                   state.getFrame(), state.getMu());

  95.         final FieldAttitude<DerivativeStructure> dsAttitude;
  96.         if (freeStateParameters > 3) {
  97.             // compute attitude partial derivatives with respect to position/velocity
  98.             dsAttitude = provider.getAttitude(dsOrbit, dsOrbit.getDate(), dsOrbit.getFrame());
  99.         } else {
  100.             // force model does not depend on attitude, don't bother recomputing it
  101.             dsAttitude = new FieldAttitude<>(factory.getDerivativeField(), state.getAttitude());
  102.         }

  104.         // initialize the list with the state having 0 formce model parameters
  105.         dsStates = new ArrayList<>();
  106.         dsStates.add(new FieldSpacecraftState<>(dsOrbit, dsAttitude, dsM));

  108.     }

  110.     /** Get the number of free state parameters.
  111.      * @return number of free state parameters
  112.      */
  113.     public int getFreeStateParameters() {
  114.         return freeStateParameters;
  115.     }

  117.     /** Get the state with the number of parameters consistent with tropospheric model.
  118.      * @param tropoModel tropospheric model
  119.      * @return state with the number of parameters consistent with tropospheric model
  120.      */
  121.     public FieldSpacecraftState<DerivativeStructure> getState(final DiscreteTroposphericModel tropoModel) {

  123.         // count the required number of parameters
  124.         int nbParams = 0;
  125.         for (final ParameterDriver driver : tropoModel.getParametersDrivers()) {
  126.             if (driver.isSelected()) {
  127.                 ++nbParams;
  128.             }
  129.         }

  131.         // fill in intermediate slots
  132.         while (dsStates.size() < nbParams + 1) {
  133.             dsStates.add(null);
  134.         }

  136.         if (dsStates.get(nbParams) == null) {
  137.             // it is the first time we need this number of parameters
  138.             // we need to create the state
  139.             final DSFactory factory = new DSFactory(freeStateParameters + nbParams, 1);
  140.             final FieldSpacecraftState<DerivativeStructure> s0 = dsStates.get(0);

  142.             // orbit
  143.             final FieldPVCoordinates<DerivativeStructure> pv0 = s0.getPVCoordinates();
  144.             final FieldOrbit<DerivativeStructure> dsOrbit =
  145.                             new FieldCartesianOrbit<>(new TimeStampedFieldPVCoordinates<>(s0.getDate().toAbsoluteDate(),
  146.                                                                                           extend(pv0.getPosition(),     factory),
  147.                                                                                           extend(pv0.getVelocity(),     factory),
  148.                                                                                           extend(pv0.getAcceleration(), factory)),
  149.                                                       s0.getFrame(), s0.getMu());

  151.             // attitude
  152.             final FieldAngularCoordinates<DerivativeStructure> ac0 = s0.getAttitude().getOrientation();
  153.             final FieldAttitude<DerivativeStructure> dsAttitude =
  154.                             new FieldAttitude<>(s0.getAttitude().getReferenceFrame(),
  155.                                                 new TimeStampedFieldAngularCoordinates<>(dsOrbit.getDate(),
  156.                                                                                          extend(ac0.getRotation(), factory),
  157.                                                                                          extend(ac0.getRotationRate(), factory),
  158.                                                                                          extend(ac0.getRotationAcceleration(), factory)));

  160.             // mass
  161.             final DerivativeStructure dsM = extend(s0.getMass(), factory);

  163.             dsStates.set(nbParams, new FieldSpacecraftState<>(dsOrbit, dsAttitude, dsM));

  165.         }

  167.         return dsStates.get(nbParams);

  169.     }

  171.     /** Add zero derivatives.
  172.      * @param original original scalar
  173.      * @param factory factory for the extended derivatives
  174.      * @return extended scalar
  175.      */
  176.     private DerivativeStructure extend(final DerivativeStructure original, final DSFactory factory) {
  177.         final double[] originalDerivatives = original.getAllDerivatives();
  178.         final double[] extendedDerivatives = new double[factory.getCompiler().getSize()];
  179.         System.arraycopy(originalDerivatives, 0, extendedDerivatives, 0, originalDerivatives.length);
  180.         return factory.build(extendedDerivatives);
  181.     }

  183.     /** Add zero derivatives.
  184.      * @param original original vector
  185.      * @param factory factory for the extended derivatives
  186.      * @return extended vector
  187.      */
  188.     private FieldVector3D<DerivativeStructure> extend(final FieldVector3D<DerivativeStructure> original, final DSFactory factory) {
  189.         return new FieldVector3D<>(extend(original.getX(), factory),
  190.                         extend(original.getY(), factory),
  191.                         extend(original.getZ(), factory));
  192.     }

  194.     /** Add zero derivatives.
  195.      * @param original original rotation
  196.      * @param factory factory for the extended derivatives
  197.      * @return extended rotation
  198.      */
  199.     private FieldRotation<DerivativeStructure> extend(final FieldRotation<DerivativeStructure> original, final DSFactory factory) {
  200.         return new FieldRotation<>(extend(original.getQ0(), factory),
  201.                         extend(original.getQ1(), factory),
  202.                         extend(original.getQ2(), factory),
  203.                         extend(original.getQ3(), factory),
  204.                         false);
  205.     }

  207.     /** Get the tropospheric model parameters.
  208.      * @param state state as returned by {@link #getState(DiscreteTroposphericModel)}
  209.      * @param tropoModel tropospheric model associated with the parameters
  210.      * @return tropospheric model parameters
  211.      */
  212.     public DerivativeStructure[] getParameters(final FieldSpacecraftState<DerivativeStructure> state,
  213.                                                final DiscreteTroposphericModel tropoModel) {
  214.         final DSFactory factory = state.getMass().getFactory();
  215.         final List<ParameterDriver> drivers = tropoModel.getParametersDrivers();
  216.         final DerivativeStructure[] parameters = new DerivativeStructure[drivers.size()];
  217.         int index = freeStateParameters;
  218.         for (int i = 0; i < drivers.size(); ++i) {
  219.             parameters[i] = drivers.get(i).isSelected() ?
  220.                             factory.variable(index++, drivers.get(i).getValue()) :
  221.                             factory.constant(drivers.get(i).getValue());
  222.         }
  223.         return parameters;
  224.     }

  226. }
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