FieldAltitudeDetector.java
- /* Copyright 2002-2022 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,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- 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;
- import org.orekit.utils.FieldPVCoordinates;
- /** 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
- */
- 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(maxCheck, threshold, DEFAULT_MAX_ITER, new FieldStopOnDecreasing<FieldAltitudeDetector<T>, T>(),
- altitude, bodyShape);
- }
- /** 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 altitude threshold altitude value (m)
- * @param bodyShape body shape with respect to which altitude should be evaluated
- * @since 6.1
- */
- private FieldAltitudeDetector(final T maxCheck, final T threshold,
- final int maxIter, final FieldEventHandler<? super FieldAltitudeDetector<T>, 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 T newMaxCheck, final T newThreshold,
- final int newMaxIter,
- final FieldEventHandler<? super FieldAltitudeDetector<T>, 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 FieldPVCoordinates<T> pvBody = s.getPVCoordinates(bodyFrame);
- final FieldGeodeticPoint<T> point = bodyShape.transform(pvBody.getPosition(),
- bodyFrame, s.getDate());
- return point.getAltitude().subtract(altitude);
- }
- }