FieldElevationDetector.java

  1. /* Copyright 2002-2018 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.events;

  19. import org.hipparchus.Field;
  20. import org.hipparchus.RealFieldElement;
  21. import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
  22. import org.hipparchus.util.FastMath;
  23. import org.orekit.errors.OrekitException;
  24. import org.orekit.frames.TopocentricFrame;
  25. import org.orekit.frames.Transform;
  26. import org.orekit.models.AtmosphericRefractionModel;
  27. import org.orekit.propagation.FieldSpacecraftState;
  28. import org.orekit.propagation.events.handlers.FieldEventHandler;
  29. import org.orekit.propagation.events.handlers.FieldStopOnDecreasing;
  30. import org.orekit.utils.ElevationMask;


  33. /**
  34.  * Finder for satellite raising/setting events that allows for the
  35.  * setting of azimuth and/or elevation bounds or a ground azimuth/elevation
  36.  * mask input. Each calculation be configured to use atmospheric refraction
  37.  * as well.
  38.  * <p>The default implementation behavior is to {@link
  39.  * org.orekit.propagation.events.handlers.FieldEventHandler.Action#CONTINUE continue}
  40.  * propagation at raising and to {@link
  41.  * org.orekit.propagation.events.handlers.FieldEventHandler.Action#STOP stop} propagation
  42.  * at setting. This can be changed by calling
  43.  * {@link #withHandler(FieldEventHandler)} after construction.</p>
  44.  * @author Hank Grabowski
  45.  */
  46. public class FieldElevationDetector<T extends RealFieldElement<T>> extends FieldAbstractDetector<FieldElevationDetector<T>, T> {

  48.     /** Elevation mask used for calculations, if defined. */
  49.     private final ElevationMask elevationMask;

  51.     /** Minimum elevation value used if mask is not defined. */
  52.     private final double minElevation;

  54.     /** Atmospheric Model used for calculations, if defined. */
  55.     private final AtmosphericRefractionModel refractionModel;

  57.     /** Topocentric frame in which elevation should be evaluated. */
  58.     private final TopocentricFrame topo;

  60.     /**
  61.      * Creates an instance of Elevation detector based on passed in topocentric frame
  62.      * and the minimum elevation angle.
  63.      * <p>
  64.      * uses default values for maximal checking interval ({@link #DEFAULT_MAXCHECK})
  65.      * and convergence threshold ({@link #DEFAULT_THRESHOLD}).</p>
  66.      * @param field type of the elements
  67.      * @param topo reference to a topocentric model
  68.      * @see #withConstantElevation(double)
  69.      * @see #withElevationMask(ElevationMask)
  70.      * @see #withRefraction(AtmosphericRefractionModel)
  71.      */
  72.     public FieldElevationDetector(final Field<T> field, final TopocentricFrame topo) {
  73.         this(field.getZero().add(DEFAULT_MAXCHECK),
  74.              field.getZero().add(DEFAULT_THRESHOLD),
  75.              topo);
  76.     }

  78.     /**
  79.      * Creates an instance of Elevation detector based on passed in topocentric frame
  80.      * and overrides of default maximal checking interval and convergence threshold values.
  81.      * @param maxCheck maximum checking interval (s)
  82.      * @param threshold maximum divergence threshold (s)
  83.      * @param topo reference to a topocentric model
  84.      * @see #withConstantElevation(double)
  85.      * @see #withElevationMask(ElevationMask)
  86.      * @see #withRefraction(AtmosphericRefractionModel)
  87.      */
  88.     public FieldElevationDetector(final T maxCheck, final T threshold, final TopocentricFrame topo) {
  89.         this(maxCheck, threshold, DEFAULT_MAX_ITER,
  90.              new FieldStopOnDecreasing<FieldElevationDetector<T>, T>(),
  91.              0.0, null, null, topo);
  92.     }

  94.     /** Private constructor with full parameters.
  95.      * <p>
  96.      * This constructor is private as users are expected to use the builder
  97.      * API with the various {@code withXxx()} methods to set up the instance
  98.      * in a readable manner without using a huge amount of parameters.
  99.      * </p>
  100.      * @param maxCheck maximum checking interval (s)
  101.      * @param threshold convergence threshold (s)
  102.      * @param maxIter maximum number of iterations in the event time search
  103.      * @param handler event handler to call at event occurrences
  104.      * @param minElevation minimum elevation in radians (rad)
  105.      * @param mask reference to elevation mask
  106.      * @param refractionModel reference to refraction model
  107.      * @param topo reference to a topocentric model
  108.      */
  109.     private FieldElevationDetector(final T maxCheck, final T threshold,
  110.                                    final int maxIter, final FieldEventHandler<? super FieldElevationDetector<T>, T> handler,
  111.                                    final double minElevation, final ElevationMask mask,
  112.                                    final AtmosphericRefractionModel refractionModel,
  113.                                    final TopocentricFrame topo) {
  114.         super(maxCheck, threshold, maxIter, handler);
  115.         this.minElevation    = minElevation;
  116.         this.elevationMask   = mask;
  117.         this.refractionModel = refractionModel;
  118.         this.topo            = topo;
  119.     }

  121.     /** {@inheritDoc} */
  122.     @Override
  123.     protected FieldElevationDetector<T> create(final T newMaxCheck, final T newThreshold,
  124.                                                final int newMaxIter, final FieldEventHandler<? super FieldElevationDetector<T>, T> newHandler) {
  125.         return new FieldElevationDetector<>(newMaxCheck, newThreshold, newMaxIter, newHandler,
  126.                                             minElevation, elevationMask, refractionModel, topo);
  127.     }

  129.     /**
  130.      * Returns the currently configured elevation mask.
  131.      * @return elevation mask
  132.      * (null if instance has been configured with {@link #withConstantElevation(double)}
  133.      * @see #withElevationMask(ElevationMask)
  134.      */
  135.     public ElevationMask getElevationMask() {
  136.         return this.elevationMask;
  137.     }

  139.     /**
  140.      * Returns the currently configured minimum valid elevation value.
  141.      * @return minimum elevation value
  142.      * ({@code Double.NaN} if instance has been configured with {@link #withElevationMask(ElevationMask)}
  143.      * @see #withConstantElevation(double)
  144.      */
  145.     public double getMinElevation() {
  146.         return this.minElevation;
  147.     }

  149.     /**
  150.      * Returns the currently configured refraction model.
  151.      * @return refraction model
  152.      * @see #withRefraction(AtmosphericRefractionModel)
  153.      */
  154.     public AtmosphericRefractionModel getRefractionModel() {
  155.         return this.refractionModel;
  156.     }

  158.     /**
  159.      * Returns the currently configured topocentric frame definitions.
  160.      * @return topocentric frame definition
  161.      */
  162.     public TopocentricFrame getTopocentricFrame() {
  163.         return this.topo;
  164.     }

  166.     /** Compute the value of the switching function.
  167.      * This function measures the difference between the current elevation
  168.      * (and azimuth if necessary) and the reference mask or minimum value.
  169.      * @param s the current state information: date, kinematics, attitude
  170.      * @return value of the switching function
  171.      * @exception OrekitException if some specific error occurs
  172.      */
  173.     @Override
  174.     public T g(final FieldSpacecraftState<T> s) throws OrekitException {

  176.         final Transform t = s.getFrame().getTransformTo(topo, s.getDate().toAbsoluteDate());
  177.         final FieldVector3D<T> extPointTopo = t.transformPosition(s.getPVCoordinates().getPosition());
  178.         final T trueElevation = extPointTopo.getDelta();

  180.         final T calculatedElevation;
  181.         if (refractionModel != null) {
  182.             calculatedElevation = trueElevation.add(refractionModel.getRefraction(trueElevation.getReal()));
  183.         } else {
  184.             calculatedElevation = trueElevation;
  185.         }

  187.         if (elevationMask != null) {
  188.             final double azimuth = FastMath.atan2(extPointTopo.getY().getReal(), extPointTopo.getX().getReal());
  189.             return calculatedElevation.subtract(elevationMask.getElevation(azimuth));
  190.         } else {
  191.             return calculatedElevation.subtract(minElevation);
  192.         }

  194.     }

  196.     /**
  197.      * Setup the minimum elevation for detection.
  198.      * <p>
  199.      * This will override an elevation mask if it has been configured as such previously.
  200.      * </p>
  201.      * @param newMinElevation minimum elevation for visibility in radians (rad)
  202.      * @return a new detector with updated configuration (the instance is not changed)
  203.      * @see #getMinElevation()
  204.      * @since 6.1
  205.      */
  206.     public FieldElevationDetector<T> withConstantElevation(final double newMinElevation) {
  207.         return new FieldElevationDetector<>(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
  208.                                             newMinElevation, null, refractionModel, topo);
  209.     }

  211.     /**
  212.      * Setup the elevation mask for detection using the passed in mask object.
  213.      * @param newElevationMask elevation mask to use for the computation
  214.      * @return a new detector with updated configuration (the instance is not changed)
  215.      * @since 6.1
  216.      * @see #getElevationMask()
  217.      */
  218.     public FieldElevationDetector<T> withElevationMask(final ElevationMask newElevationMask) {
  219.         return new FieldElevationDetector<>(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
  220.                                             Double.NaN, newElevationMask, refractionModel, topo);
  221.     }

  223.     /**
  224.      * Setup the elevation detector to use an atmospheric refraction model in its
  225.      * calculations.
  226.      * <p>
  227.      * To disable the refraction when copying an existing elevation
  228.      * detector, call this method with a null argument.
  229.      * </p>
  230.      * @param newRefractionModel refraction model to use for the computation
  231.      * @return a new detector with updated configuration (the instance is not changed)
  232.      * @since 6.1
  233.      * @see #getRefractionModel()
  234.      */
  235.     public FieldElevationDetector<T> withRefraction(final AtmosphericRefractionModel newRefractionModel) {
  236.         return new FieldElevationDetector<>(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
  237.                                             minElevation, elevationMask, newRefractionModel, topo);
  238.     }

  240. }
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