FieldOfViewDetector.java
/* Copyright 2002-2019 CS Systèmes d'Information
* Licensed to CS Systèmes d'Information (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
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* See the License for the specific language governing permissions and
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*/
package org.orekit.propagation.events;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.hipparchus.ode.events.Action;
import org.hipparchus.util.FastMath;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.handlers.EventHandler;
import org.orekit.propagation.events.handlers.StopOnIncreasing;
import org.orekit.utils.PVCoordinatesProvider;
/** Finder for target entry/exit events with respect to a satellite sensor
* {@link FieldOfView Field Of View}.
* <p>The default implementation behavior is to {@link Action#CONTINUE continue}
* propagation at FOV entry and to {@link Action#STOP stop} propagation
* at FOV exit. This can be changed by calling
* {@link #withHandler(EventHandler)} after construction.</p>
* @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
* @see CircularFieldOfViewDetector
* @see FootprintOverlapDetector
* @see VisibilityTrigger
* @author Luc Maisonobe
* @since 7.1
*/
public class FieldOfViewDetector extends AbstractDetector<FieldOfViewDetector> {
/** Position/velocity provider of the considered target. */
private final PVCoordinatesProvider targetPVProvider;
/** Radius of the target, considered to be a spherical body (m). */
private final double radiusTarget;
/** Visibility trigger for spherical bodies. */
private final VisibilityTrigger trigger;
/** Field of view. */
private final FieldOfView fov;
/** Build a new instance.
* <p>The maximal interval between distance to FOV boundary checks should
* be smaller than the half duration of the minimal pass to handle,
* otherwise some short passes could be missed.</p>
* @param pvTarget Position/velocity provider of the considered target
* @param fov Field Of View
*/
public FieldOfViewDetector(final PVCoordinatesProvider pvTarget, final FieldOfView fov) {
this(pvTarget, 0.0, VisibilityTrigger.VISIBLE_AS_SOON_AS_PARTIALLY_IN_FOV, fov);
}
/** Build a new instance.
* <p>The maximal interval between distance to FOV boundary checks should
* be smaller than the half duration of the minimal pass to handle,
* otherwise some short passes could be missed.</p>
* @param pvTarget Position/velocity provider of the considered target
* @param radiusTarget radius of the target, considered to be a spherical body (m)
* @param trigger visibility trigger for spherical bodie
* @param fov Field Of View
* @since 10.0
*/
public FieldOfViewDetector(final PVCoordinatesProvider pvTarget, final double radiusTarget,
final VisibilityTrigger trigger, final FieldOfView fov) {
this(DEFAULT_MAXCHECK, DEFAULT_THRESHOLD, DEFAULT_MAX_ITER,
new StopOnIncreasing<FieldOfViewDetector>(),
pvTarget, radiusTarget, trigger, fov);
}
/** Private constructor with full parameters.
* <p>
* This constructor is private as users are expected to use the builder
* API with the various {@code withXxx()} methods to set up the instance
* in a readable manner without using a huge amount of parameters.
* </p>
* @param maxCheck maximum checking interval (s)
* @param threshold convergence threshold (s)
* @param maxIter maximum number of iterations in the event time search
* @param handler event handler to call at event occurrences
* @param pvTarget Position/velocity provider of the considered target
* @param radiusTarget radius of the target, considered to be a spherical body (m)
* @param trigger visibility trigger for spherical bodie
* @param fov Field Of View
*/
private FieldOfViewDetector(final double maxCheck, final double threshold, final int maxIter,
final EventHandler<? super FieldOfViewDetector> handler,
final PVCoordinatesProvider pvTarget, final double radiusTarget,
final VisibilityTrigger trigger, final FieldOfView fov) {
super(maxCheck, threshold, maxIter, handler);
this.targetPVProvider = pvTarget;
this.radiusTarget = radiusTarget;
this.trigger = trigger;
this.fov = fov;
}
/** {@inheritDoc} */
@Override
protected FieldOfViewDetector create(final double newMaxCheck, final double newThreshold,
final int newMaxIter,
final EventHandler<? super FieldOfViewDetector> newHandler) {
return new FieldOfViewDetector(newMaxCheck, newThreshold, newMaxIter, newHandler,
targetPVProvider, radiusTarget, trigger, fov);
}
/** Get the position/velocity provider of the target .
* @return the position/velocity provider of the target
*/
public PVCoordinatesProvider getPVTarget() {
return targetPVProvider;
}
/** Get the Field Of View.
* @return Field Of View
*/
public FieldOfView getFieldOfView() {
return fov;
}
/** {@inheritDoc}
* <p>
* The g function value is the angular offset between the
* target center and the {@link FieldOfView#offsetFromBoundary(Vector3D)
* Field Of View boundary}, plus or minus the target angular radius
* depending on the {@link VisibilityTrigger}, minus the {@link
* FieldOfView#getMargin() Field Of View margin}. It is therefore negative
* if the target is visible within the Field Of View and positive if it is
* outside of the Field Of View.
* </p>
* <p>
* As per the previous definition, when the target enters the Field Of
* View, a decreasing event is generated, and when the target leaves
* the Field Of View, an increasing event is generated.
* </p>
*/
public double g(final SpacecraftState s) {
// get line of sight in spacecraft frame
final Vector3D targetPosInert =
targetPVProvider.getPVCoordinates(s.getDate(), s.getFrame()).getPosition();
final Vector3D lineOfSightSC = s.toTransform().transformPosition(targetPosInert);
final double angularRadius = FastMath.asin(radiusTarget / lineOfSightSC.getNorm());
return fov.offsetFromBoundary(lineOfSightSC) + FastMath.copySign(angularRadius, trigger.getSign());
}
}