FieldAltitudeDetector.java
/* Copyright 2002-2023 CS GROUP
* Licensed to CS GROUP (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
* the License. You may obtain a copy of the License at
*
* 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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package org.orekit.propagation.events;
import org.hipparchus.CalculusFieldElement;
import org.hipparchus.ode.events.Action;
import org.orekit.bodies.BodyShape;
import org.orekit.bodies.FieldGeodeticPoint;
import org.orekit.frames.Frame;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.events.handlers.FieldEventHandler;
import org.orekit.propagation.events.handlers.FieldStopOnDecreasing;
/** Finder for satellite altitude crossing events.
* <p>This class finds altitude events (i.e. satellite crossing
* a predefined altitude level above ground).</p>
* <p>The default implementation behavior is to {@link Action#CONTINUE
* continue} propagation when ascending and to {@link Action#STOP stop}
* propagation when descending. This can be changed by calling
* {@link #withHandler(FieldEventHandler)} after construction.</p>
* @see org.orekit.propagation.FieldPropagator#addEventDetector(FieldEventDetector)
* @author Luc Maisonobe
* @since 9.0
* @param <T> type of the field elements
*/
public class FieldAltitudeDetector<T extends CalculusFieldElement<T>> extends FieldAbstractDetector<FieldAltitudeDetector<T>, T> {
/** Threshold altitude value (m). */
private final T altitude;
/** Body shape with respect to which altitude should be evaluated. */
private final BodyShape bodyShape;
/** Build a new altitude detector.
* <p>This simple constructor takes default values for maximal checking
* interval ({@link #DEFAULT_MAXCHECK}) and convergence threshold
* ({@link #DEFAULT_THRESHOLD}).</p>
* @param altitude threshold altitude value
* @param bodyShape body shape with respect to which altitude should be evaluated
*/
public FieldAltitudeDetector(final T altitude, final BodyShape bodyShape) {
this(altitude.getField().getZero().add(DEFAULT_MAXCHECK),
altitude.getField().getZero().add(DEFAULT_THRESHOLD),
altitude, bodyShape);
}
/** Build a new altitude detector.
* <p>This simple constructor takes default value for convergence threshold
* ({@link #DEFAULT_THRESHOLD}).</p>
* <p>The maximal interval between altitude 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 checking interval (s)
* @param altitude threshold altitude value (m)
* @param bodyShape body shape with respect to which altitude should be evaluated
*/
public FieldAltitudeDetector(final T maxCheck,
final T altitude,
final BodyShape bodyShape) {
this(maxCheck, altitude.getField().getZero().add(DEFAULT_THRESHOLD), altitude, bodyShape);
}
/** Build a new altitude detector.
* <p>The maximal interval between altitude checks should
* be smaller than the half duration of the minimal pass to handle,
* otherwise some short passes could be missed.</p>
* <p>The maximal interval between altitude 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 checking interval (s)
* @param threshold convergence threshold (s)
* @param altitude threshold altitude value (m)
* @param bodyShape body shape with respect to which altitude should be evaluated
*/
public FieldAltitudeDetector(final T maxCheck,
final T threshold,
final T altitude,
final BodyShape bodyShape) {
this(s -> maxCheck.getReal(), threshold, DEFAULT_MAX_ITER, new FieldStopOnDecreasing<T>(),
altitude, bodyShape);
}
/** Protected constructor with full parameters.
* <p>
* This constructor is not public 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
* @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 altitude threshold altitude value (m)
* @param bodyShape body shape with respect to which altitude should be evaluated
* @since 6.1
*/
protected FieldAltitudeDetector(final FieldAdaptableInterval<T> maxCheck, final T threshold,
final int maxIter, final FieldEventHandler<T> handler,
final T altitude,
final BodyShape bodyShape) {
super(maxCheck, threshold, maxIter, handler);
this.altitude = altitude;
this.bodyShape = bodyShape;
}
/** {@inheritDoc} */
@Override
protected FieldAltitudeDetector<T> create(final FieldAdaptableInterval<T> newMaxCheck, final T newThreshold,
final int newMaxIter,
final FieldEventHandler<T> newHandler) {
return new FieldAltitudeDetector<>(newMaxCheck, newThreshold, newMaxIter, newHandler,
altitude, bodyShape);
}
/** Get the threshold altitude value.
* @return the threshold altitude value (m)
*/
public T getAltitude() {
return altitude;
}
/** Get the body shape.
* @return the body shape
*/
public BodyShape getBodyShape() {
return bodyShape;
}
/** Compute the value of the switching function.
* This function measures the difference between the current altitude
* and the threshold altitude.
* @param s the current state information: date, kinematics, attitude
* @return value of the switching function
*/
public T g(final FieldSpacecraftState<T> s) {
final Frame bodyFrame = bodyShape.getBodyFrame();
final FieldGeodeticPoint<T> point = bodyShape.transform(s.getPosition(bodyFrame),
bodyFrame, s.getDate());
return point.getAltitude().subtract(altitude);
}
}