TODProvider.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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* See the License for the specific language governing permissions and
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*/
package org.orekit.frames;
import java.io.Serializable;
import org.hipparchus.CalculusFieldElement;
import org.hipparchus.geometry.euclidean.threed.FieldRotation;
import org.hipparchus.geometry.euclidean.threed.Rotation;
import org.hipparchus.geometry.euclidean.threed.RotationConvention;
import org.hipparchus.geometry.euclidean.threed.RotationOrder;
import org.orekit.annotation.DefaultDataContext;
import org.orekit.data.DataContext;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitInternalError;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.time.TimeScalarFunction;
import org.orekit.time.TimeScales;
import org.orekit.time.TimeVectorFunction;
import org.orekit.utils.IERSConventions;
/** Provider for True of Date (ToD) frame.
* <p>This frame handles nutation effects according to selected IERS conventions.</p>
* <p>Transform is computed with reference to the {@link MODProvider Mean of Date} frame.</p>
* @author Pascal Parraud
*/
class TODProvider implements EOPBasedTransformProvider {
/** Serializable UID. */
private static final long serialVersionUID = 20131209L;
/** Conventions. */
private final IERSConventions conventions;
/** EOP history. */
private final EOPHistory eopHistory;
/** Function computing the mean obliquity. */
private final transient TimeScalarFunction obliquityFunction;
/** Function computing the nutation angles. */
private final transient TimeVectorFunction nutationFunction;
/**
* Simple constructor.
* @param conventions IERS conventions to apply
* @param eopHistory EOP history, or {@code null} if no correction should be
* applied.
* @param timeScales TAI time scale.
*/
TODProvider(final IERSConventions conventions,
final EOPHistory eopHistory,
final TimeScales timeScales) {
this.conventions = conventions;
this.eopHistory = eopHistory;
this.obliquityFunction = conventions.getMeanObliquityFunction(timeScales);
this.nutationFunction =
conventions.getNutationFunction(timeScales);
}
/**
* Private constructor.
*
* @param conventions IERS conventions to use.
* @param eopHistory or {@code null} if no correction should be applied.
* @param obliquityFunction to use.
* @param nutationFunction to use.
*/
private TODProvider(final IERSConventions conventions,
final EOPHistory eopHistory,
final TimeScalarFunction obliquityFunction,
final TimeVectorFunction nutationFunction) {
this.conventions = conventions;
this.eopHistory = eopHistory;
this.obliquityFunction = obliquityFunction;
this.nutationFunction = nutationFunction;
}
/** {@inheritDoc} */
@Override
public EOPHistory getEOPHistory() {
return eopHistory;
}
/** {@inheritDoc} */
@Override
public TODProvider getNonInterpolatingProvider() {
return new TODProvider(conventions, eopHistory.getEOPHistoryWithoutCachedTidalCorrection(),
obliquityFunction, nutationFunction);
}
/** {@inheritDoc} */
@Override
public Transform getTransform(final AbsoluteDate date) {
// compute nutation angles
final double[] angles = nutationFunction.value(date);
// compute the mean obliquity of the ecliptic
final double moe = obliquityFunction.value(date);
double dpsi = angles[0];
double deps = angles[1];
if (eopHistory != null) {
// apply the corrections for the nutation parameters
final double[] correction = eopHistory.getEquinoxNutationCorrection(date);
dpsi += correction[0];
deps += correction[1];
}
// compute the true obliquity of the ecliptic
final double toe = moe + deps;
// complete nutation
final Rotation nutation = new Rotation(RotationOrder.XZX, RotationConvention.FRAME_TRANSFORM,
moe, -dpsi, -toe);
// set up the transform from parent MOD
return new Transform(date, nutation);
}
/** Replace the instance with a data transfer object for serialization.
/** {@inheritDoc} */
@Override
public <T extends CalculusFieldElement<T>> FieldTransform<T> getTransform(final FieldAbsoluteDate<T> date) {
// compute nutation angles
final T[] angles = nutationFunction.value(date);
// compute the mean obliquity of the ecliptic
final T moe = obliquityFunction.value(date);
T dpsi = angles[0];
T deps = angles[1];
if (eopHistory != null) {
// apply the corrections for the nutation parameters
final T[] correction = eopHistory.getEquinoxNutationCorrection(date);
dpsi = dpsi.add(correction[0]);
deps = deps.add(correction[1]);
}
// compute the true obliquity of the ecliptic
final T toe = moe.add(deps);
// complete nutation
final FieldRotation<T> nutation = new FieldRotation<>(RotationOrder.XZX, RotationConvention.FRAME_TRANSFORM,
moe, dpsi.negate(), toe.negate());
// set up the transform from parent MOD
return new FieldTransform<>(date, nutation);
}
/** Replace the instance with a data transfer object for serialization.
* <p>
* This intermediate class serializes only the frame key.
* </p>
* @return data transfer object that will be serialized
*/
@DefaultDataContext
private Object writeReplace() {
return new DataTransferObject(conventions, eopHistory);
}
/** Internal class used only for serialization. */
@DefaultDataContext
private static class DataTransferObject implements Serializable {
/** Serializable UID. */
private static final long serialVersionUID = 20131209L;
/** Conventions. */
private final IERSConventions conventions;
/** EOP history. */
private final EOPHistory eopHistory;
/** Simple constructor.
* @param conventions IERS conventions to apply
* @param eopHistory EOP history
*/
DataTransferObject(final IERSConventions conventions, final EOPHistory eopHistory) {
this.conventions = conventions;
this.eopHistory = eopHistory;
}
/** Replace the deserialized data transfer object with a {@link TODProvider}.
* @return replacement {@link TODProvider}
*/
private Object readResolve() {
try {
// retrieve a managed frame
return new TODProvider(conventions, eopHistory,
DataContext.getDefault().getTimeScales());
} catch (OrekitException oe) {
throw new OrekitInternalError(oe);
}
}
}
}