FieldLongitudeExtremumDetector.java

/* Copyright 2022-2025 Romain Serra
 * 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.Field;
import org.hipparchus.analysis.differentiation.FieldUnivariateDerivative2;
import org.orekit.bodies.BodyShape;
import org.orekit.bodies.FieldGeodeticPoint;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.events.handlers.FieldEventHandler;
import org.orekit.propagation.events.handlers.FieldStopOnIncreasing;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.utils.FieldPVCoordinates;

/** Detector for longitude extrema.
 * @author Romain Serra
 * @since 14.0
 * @see LongitudeExtremumDetector
 * @param <T> type of the field elements
 */
public class FieldLongitudeExtremumDetector<T extends CalculusFieldElement<T>>
        extends FieldAbstractGeographicalDetector<FieldLongitudeExtremumDetector<T>, T> {

    /** Build a new detector.
     * <p>The new instance uses default values for maximal checking interval
     * ({@link #DEFAULT_MAX_CHECK}) and convergence threshold ({@link
     * #DEFAULT_THRESHOLD}).</p>
     * @param field the type of numbers to use.
     * @param body body on which the longitude is defined
     */
    public FieldLongitudeExtremumDetector(final Field<T> field, final BodyShape body) {
        this(new FieldEventDetectionSettings<>(field, EventDetectionSettings.getDefaultEventDetectionSettings()),
                new FieldStopOnIncreasing<>(), body);
    }

    /** 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 detectionSettings event detection settings
     * @param handler event handler to call at event occurrences
     * @param body body on which the longitude is defined
     * @since 13.0
     */
    public FieldLongitudeExtremumDetector(final FieldEventDetectionSettings<T> detectionSettings,
                                          final FieldEventHandler<T> handler, final BodyShape body) {
        super(detectionSettings, handler, body);
    }

    /** {@inheritDoc} */
    @Override
    protected FieldLongitudeExtremumDetector<T> create(final FieldEventDetectionSettings<T> detectionSettings,
                                                       final FieldEventHandler<T> newHandler) {
        return new FieldLongitudeExtremumDetector<>(detectionSettings, newHandler, getBodyShape());
    }

    @Override
    public T g(final FieldSpacecraftState<T> s) {
        // convert state to geodetic coordinates
        final FieldAbsoluteDate<FieldUnivariateDerivative2<T>> fud2Date = s.getDate().toFUD2Field();
        final FieldPVCoordinates<FieldUnivariateDerivative2<T>> pv = s.getPVCoordinates().toUnivariateDerivative2PV();
        final FieldGeodeticPoint<FieldUnivariateDerivative2<T>> gp = getBodyShape().transform(pv.getPosition(), s.getFrame(), fud2Date);

        // longitude rate
        return gp.getLongitude().getFirstDerivative();

    }

}