CircularFieldOfViewDetector.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
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*
* http://www.apache.org/licenses/LICENSE-2.0
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* 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.StopOnDecreasing;
import org.orekit.utils.PVCoordinatesProvider;
/** Finder for target entry/exit events with respect to a satellite sensor Field Of View.
* <p>This class handle fields of view with a circular boundary.</p>
* <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 FieldOfViewDetector
* @see VisibilityTrigger
* @author Véronique Pommier-Maurussane
*/
public class CircularFieldOfViewDetector extends AbstractDetector<CircularFieldOfViewDetector> {
/** 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;
/** Direction of the FOV center. */
private final Vector3D center;
/** FOV half aperture angle. */
private final double halfAperture;
/** 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 maxCheck maximal interval in seconds
* @param pvTarget Position/velocity provider of the considered target
* @param center Direction of the FOV center, in spacecraft frame
* @param halfAperture FOV half aperture angle
*/
public CircularFieldOfViewDetector(final double maxCheck,
final PVCoordinatesProvider pvTarget,
final Vector3D center,
final double halfAperture) {
this(maxCheck, pvTarget, 0.0, VisibilityTrigger.VISIBLE_AS_SOON_AS_PARTIALLY_IN_FOV, center, halfAperture);
}
/** 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 maxCheck maximal interval in seconds
* @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 center Direction of the FOV center, in spacecraft frame
* @param halfAperture FOV half aperture angle
* @since 10.0
*/
public CircularFieldOfViewDetector(final double maxCheck,
final PVCoordinatesProvider pvTarget, final double radiusTarget,
final VisibilityTrigger trigger, final Vector3D center, final double halfAperture) {
this(maxCheck, 1.0e-3, DEFAULT_MAX_ITER, new StopOnDecreasing<CircularFieldOfViewDetector>(),
pvTarget, radiusTarget, trigger, center, halfAperture);
}
/** 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 center Direction of the FOV center, in spacecraft frame
* @param halfAperture FOV half aperture angle
* @since 6.1
*/
private CircularFieldOfViewDetector(final double maxCheck, final double threshold,
final int maxIter, final EventHandler<? super CircularFieldOfViewDetector> handler,
final PVCoordinatesProvider pvTarget, final double radiusTarget,
final VisibilityTrigger trigger, final Vector3D center, final double halfAperture) {
super(maxCheck, threshold, maxIter, handler);
this.targetPVProvider = pvTarget;
this.radiusTarget = radiusTarget;
this.trigger = trigger;
this.center = center;
this.halfAperture = halfAperture;
}
/** {@inheritDoc} */
@Override
protected CircularFieldOfViewDetector create(final double newMaxCheck, final double newThreshold,
final int newMaxIter, final EventHandler<? super CircularFieldOfViewDetector> newHandler) {
return new CircularFieldOfViewDetector(newMaxCheck, newThreshold, newMaxIter, newHandler,
targetPVProvider, radiusTarget, trigger, center, halfAperture);
}
/** Get the position/velocity provider of the target .
* @return the position/velocity provider of the target
*/
public PVCoordinatesProvider getPVTarget() {
return targetPVProvider;
}
/** Get the direction of FOV center.
* @return the direction of FOV center
*/
public Vector3D getCenter() {
return center;
}
/** Get FOV half aperture angle.
* @return the FOV half aperture angle
*/
public double getHalfAperture() {
return halfAperture;
}
/** {@inheritDoc}
* <p>
* The g function value is the difference between FOV half aperture and the
* absolute value of the angle between target direction and field of view center,
* plus or minus the target angular radius depending on the {@link VisibilityTrigger}.
* It is positive inside the FOV and negative outside.
* </p>
*/
public double g(final SpacecraftState s) {
// Compute target position/velocity at date in spacecraft frame
final Vector3D targetPosInert = new Vector3D(1, targetPVProvider.getPVCoordinates(s.getDate(), s.getFrame()).getPosition(),
-1, s.getPVCoordinates().getPosition());
final Vector3D targetPosSat = s.getAttitude().getRotation().applyTo(targetPosInert);
final double angularRadius = FastMath.asin(radiusTarget / targetPosSat.getNorm());
// Target is in the field of view if the absolute value that angle is smaller than FOV half aperture.
// g function value is the difference between FOV half aperture and the absolute value of the angle between
// target direction and field of view center. It is positive inside the FOV and negative outside.
return halfAperture - Vector3D.angle(targetPosSat, center) - FastMath.copySign(angularRadius, trigger.getSign());
}
}