AbstractPropagatorBuilder.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.propagation.conversion;

  19. import java.util.List;

  21. import org.hipparchus.exception.LocalizedCoreFormats;
  22. import org.hipparchus.util.FastMath;
  23. import org.orekit.errors.OrekitIllegalArgumentException;
  24. import org.orekit.forces.gravity.NewtonianAttraction;
  25. import org.orekit.frames.Frame;
  26. import org.orekit.orbits.Orbit;
  27. import org.orekit.orbits.OrbitType;
  28. import org.orekit.orbits.PositionAngle;
  29. import org.orekit.time.AbsoluteDate;
  30. import org.orekit.utils.ParameterDriver;
  31. import org.orekit.utils.ParameterDriversList;
  32. import org.orekit.utils.ParameterDriversList.DelegatingDriver;
  33. import org.orekit.utils.ParameterObserver;

  35. /** Base class for propagator builders.
  36.  * @author Pascal Parraud
  37.  * @since 7.1
  38.  */
  39. public abstract class AbstractPropagatorBuilder implements PropagatorBuilder {

  41.     /** Central attraction scaling factor.
  42.      * <p>
  43.      * We use a power of 2 to avoid numeric noise introduction
  44.      * in the multiplications/divisions sequences.
  45.      * </p>
  46.      */
  47.     private static final double MU_SCALE = FastMath.scalb(1.0, 32);

  49.     /** Date of the initial orbit. */
  50.     private AbsoluteDate initialOrbitDate;

  52.     /** Frame in which the orbit is propagated. */
  53.     private final Frame frame;

  55.     /** Central attraction coefficient (m³/s²). */
  56.     private double mu;

  58.     /** Drivers for orbital parameters. */
  59.     private final ParameterDriversList orbitalDrivers;

  61.     /** List of the supported parameters. */
  62.     private ParameterDriversList propagationDrivers;

  64.     /** Orbit type to use. */
  65.     private final OrbitType orbitType;

  67.     /** Position angle type to use. */
  68.     private final PositionAngle positionAngle;

  70.     /** Position scale to use for the orbital drivers. */
  71.     private final double positionScale;

  73.     /** Build a new instance.
  74.      * <p>
  75.      * The template orbit is used as a model to {@link
  76.      * #createInitialOrbit() create initial orbit}. It defines the
  77.      * inertial frame, the central attraction coefficient, the orbit type, and is also
  78.      * used together with the {@code positionScale} to convert from the {@link
  79.      * ParameterDriver#setNormalizedValue(double) normalized} parameters used by the
  80.      * callers of this builder to the real orbital parameters.
  81.      * </p>
  82.      * <p>
  83.      * By default, all the {@link #getOrbitalParametersDrivers() orbital parameters drivers}
  84.      * are selected, which means that if the builder is used for orbit determination or
  85.      * propagator conversion, all orbital parameters will be estimated. If only a subset
  86.      * of the orbital parameters must be estimated, caller must retrieve the orbital
  87.      * parameters by calling {@link #getOrbitalParametersDrivers()} and then call
  88.      * {@link ParameterDriver#setSelected(boolean) setSelected(false)}.
  89.      * </p>
  90.      * @param templateOrbit reference orbit from which real orbits will be built
  91.      * @param positionAngle position angle type to use
  92.      * @param positionScale scaling factor used for orbital parameters normalization
  93.      * (typically set to the expected standard deviation of the position)
  94.      * @param addDriverForCentralAttraction if true, a {@link ParameterDriver} should
  95.      * be set up for central attraction coefficient
  96.           * @since 8.0
  97.      */
  98.     protected AbstractPropagatorBuilder(final Orbit templateOrbit, final PositionAngle positionAngle,
  99.                                         final double positionScale, final boolean addDriverForCentralAttraction) {

  101.         this.initialOrbitDate    = templateOrbit.getDate();
  102.         this.frame               = templateOrbit.getFrame();
  103.         this.mu                  = templateOrbit.getMu();
  104.         this.propagationDrivers  = new ParameterDriversList();
  105.         this.orbitType           = templateOrbit.getType();
  106.         this.positionAngle       = positionAngle;
  107.         this.positionScale       = positionScale;
  108.         this.orbitalDrivers      = orbitType.getDrivers(positionScale, templateOrbit, positionAngle);
  109.         for (final DelegatingDriver driver : orbitalDrivers.getDrivers()) {
  110.             driver.setSelected(true);
  111.         }

  113.         if (addDriverForCentralAttraction) {
  114.             final ParameterDriver muDriver = new ParameterDriver(NewtonianAttraction.CENTRAL_ATTRACTION_COEFFICIENT,
  115.                                                                  mu, MU_SCALE, 0, Double.POSITIVE_INFINITY);
  116.             muDriver.addObserver(new ParameterObserver() {
  117.                 /** {@inheridDoc} */
  118.                 @Override
  119.                 public void valueChanged(final double previousValue, final ParameterDriver driver) {
  120.                     AbstractPropagatorBuilder.this.mu = driver.getValue();
  121.                 }
  122.             });
  123.             propagationDrivers.add(muDriver);
  124.         }

  126.     }

  128.     /** {@inheritDoc} */
  129.     public OrbitType getOrbitType() {
  130.         return orbitType;
  131.     }

  133.     /** {@inheritDoc} */
  134.     public PositionAngle getPositionAngle() {
  135.         return positionAngle;
  136.     }

  138.     /** {@inheritDoc} */
  139.     public AbsoluteDate getInitialOrbitDate() {
  140.         return initialOrbitDate;
  141.     }

  143.     /** {@inheritDoc} */
  144.     public Frame getFrame() {
  145.         return frame;
  146.     }

  148.     /** {@inheritDoc} */
  149.     public ParameterDriversList getOrbitalParametersDrivers() {
  150.         return orbitalDrivers;
  151.     }

  153.     /** {@inheritDoc} */
  154.     public ParameterDriversList getPropagationParametersDrivers() {
  155.         return propagationDrivers;
  156.     }

  158.     /** Get the position scale.
  159.      * @return the position scale used to scale the orbital drivers
  160.      */
  161.     public double getPositionScale() {
  162.         return positionScale;
  163.     }

  165.     /** Get the central attraction coefficient (µ - m³/s²) value.
  166.      * @return the central attraction coefficient (µ - m³/s²) value
  167.      * @since 9.2
  168.      */
  169.     public double getMu() {
  170.         return mu;
  171.     }

  173.     /** Get the number of selected parameters.
  174.      * @return number of selected parameters
  175.      */
  176.     private int getNbSelected() {

  178.         int count = 0;

  180.         // count orbital parameters
  181.         for (final ParameterDriver driver : orbitalDrivers.getDrivers()) {
  182.             if (driver.isSelected()) {
  183.                 ++count;
  184.             }
  185.         }

  187.         // count propagation parameters
  188.         for (final ParameterDriver driver : propagationDrivers.getDrivers()) {
  189.             if (driver.isSelected()) {
  190.                 ++count;
  191.             }
  192.         }

  194.         return count;

  196.     }

  198.     /** {@inheritDoc} */
  199.     public double[] getSelectedNormalizedParameters() {

  201.         // allocate array
  202.         final double[] selected = new double[getNbSelected()];

  204.         // fill data
  205.         int index = 0;
  206.         for (final ParameterDriver driver : orbitalDrivers.getDrivers()) {
  207.             if (driver.isSelected()) {
  208.                 selected[index++] = driver.getNormalizedValue();
  209.             }
  210.         }
  211.         for (final ParameterDriver driver : propagationDrivers.getDrivers()) {
  212.             if (driver.isSelected()) {
  213.                 selected[index++] = driver.getNormalizedValue();
  214.             }
  215.         }

  217.         return selected;

  219.     }

  221.     /** Build an initial orbit using the current selected parameters.
  222.      * <p>
  223.      * This method is a stripped down version of {@link #buildPropagator(double[])}
  224.      * that only builds the initial orbit and not the full propagator.
  225.      * </p>
  226.      * @return an initial orbit
  227.      * @since 8.0
  228.      */
  229.     protected Orbit createInitialOrbit() {
  230.         final double[] unNormalized = new double[orbitalDrivers.getNbParams()];
  231.         for (int i = 0; i < unNormalized.length; ++i) {
  232.             unNormalized[i] = orbitalDrivers.getDrivers().get(i).getValue();
  233.         }
  234.         return getOrbitType().mapArrayToOrbit(unNormalized, null, positionAngle, initialOrbitDate, mu, frame);
  235.     }

  237.     /** Set the selected parameters.
  238.      * @param normalizedParameters normalized values for the selected parameters
  239.      */
  240.     protected void setParameters(final double[] normalizedParameters) {


  243.         if (normalizedParameters.length != getNbSelected()) {
  244.             throw new OrekitIllegalArgumentException(LocalizedCoreFormats.DIMENSIONS_MISMATCH,
  245.                                                      normalizedParameters.length,
  246.                                                      getNbSelected());
  247.         }

  249.         int index = 0;

  251.         // manage orbital parameters
  252.         for (final ParameterDriver driver : orbitalDrivers.getDrivers()) {
  253.             if (driver.isSelected()) {
  254.                 driver.setNormalizedValue(normalizedParameters[index++]);
  255.             }
  256.         }

  258.         // manage propagation parameters
  259.         for (final ParameterDriver driver : propagationDrivers.getDrivers()) {
  260.             if (driver.isSelected()) {
  261.                 driver.setNormalizedValue(normalizedParameters[index++]);
  262.             }
  263.         }

  265.     }

  267.     /** Add a supported parameter.
  268.      * @param driver driver for the parameter
  269.      */
  270.     protected void addSupportedParameter(final ParameterDriver driver) {
  271.         propagationDrivers.add(driver);
  272.         propagationDrivers.sort();
  273.     }

  275.     /** Reset the orbit in the propagator builder.
  276.      * @param newOrbit New orbit to set in the propagator builder
  277.      */
  278.     public void resetOrbit(final Orbit newOrbit) {

  280.         // Map the new orbit in an array of double
  281.         final double[] orbitArray = new double[6];
  282.         orbitType.mapOrbitToArray(newOrbit, getPositionAngle(), orbitArray, null);

  284.         // Update all the orbital drivers, selected or unselected
  285.         // Reset values and reference values
  286.         final List<DelegatingDriver> orbitalDriversList = getOrbitalParametersDrivers().getDrivers();
  287.         int i = 0;
  288.         for (DelegatingDriver driver : orbitalDriversList) {
  289.             driver.setReferenceValue(orbitArray[i]);
  290.             driver.setValue(orbitArray[i++]);
  291.         }

  293.         // Change the initial orbit date in the builder
  294.         this.initialOrbitDate = newOrbit.getDate();
  295.     }
  296. }
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