/* Copyright 2002-2017 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
* (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.frames;
import java.io.Serializable;
import org.hipparchus.RealFieldElement;
import org.hipparchus.geometry.euclidean.threed.FieldRotation;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Rotation;
import org.hipparchus.geometry.euclidean.threed.RotationConvention;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
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.TimeScalesFactory;
import org.orekit.time.UT1Scale;
import org.orekit.utils.Constants;
import org.orekit.utils.IERSConventions;
/** Greenwich True Of Date Frame, also known as True of Date Rotating frame (TDR)
* or Greenwich Rotating Coordinate frame (GCR).
* <p> This frame handles the sidereal time according to IAU-82 model.</p>
* <p> Its parent frame is the {@link TODProvider}.</p>
* <p> The pole motion is not applied here.</p>
* @author Pascal Parraud
* @author Thierry Ceolin
*/
public class GTODProvider implements EOPBasedTransformProvider {
/** Serializable UID. */
private static final long serialVersionUID = 20141228L;
/** Angular velocity of the Earth, in rad/s. */
private static final double AVE = 7.292115146706979e-5;
/** Conventions. */
private final IERSConventions conventions;
/** EOP history. */
private final EOPHistory eopHistory;
/** GAST function. */
private final transient TimeScalarFunction gastFunction;
/** Simple constructor.
* @param conventions IERS conventions to use
* @param eopHistory EOP history (may be null)
* @exception OrekitException if EOP parameters are desired but cannot be read
*/
protected GTODProvider(final IERSConventions conventions, final EOPHistory eopHistory)
throws OrekitException {
final UT1Scale ut1 = TimeScalesFactory.getUT1(eopHistory);
this.conventions = conventions;
this.eopHistory = eopHistory;
this.gastFunction = conventions.getGASTFunction(ut1, eopHistory);
}
/** {@inheritDoc} */
@Override
public EOPHistory getEOPHistory() {
return eopHistory;
}
/** {@inheritDoc} */
@Override
public GTODProvider getNonInterpolatingProvider()
throws OrekitException {
return new GTODProvider(conventions, eopHistory.getNonInterpolatingEOPHistory());
}
/** {@inheritDoc} */
@Override
public Transform getTransform(final AbsoluteDate date) throws OrekitException {
// compute Greenwich apparent sidereal time, in radians
final double gast = gastFunction.value(date);
// compute true angular rotation of Earth, in rad/s
final double lod = (eopHistory == null) ? 0.0 : eopHistory.getLOD(date);
final double omp = AVE * (1 - lod / Constants.JULIAN_DAY);
final Vector3D rotationRate = new Vector3D(omp, Vector3D.PLUS_K);
// set up the transform from parent TOD
return new Transform(date, new Rotation(Vector3D.PLUS_K, gast, RotationConvention.FRAME_TRANSFORM), rotationRate);
}
/** {@inheritDoc} */
@Override
public <T extends RealFieldElement<T>> FieldTransform<T> getTransform(final FieldAbsoluteDate<T> date) {
// compute Greenwich apparent sidereal time, in radians
final T gast = gastFunction.value(date);
// compute true angular rotation of Earth, in rad/s
final T lod = (eopHistory == null) ? date.getField().getZero() : eopHistory.getLOD(date);
final T omp = lod.multiply(-1.0 / Constants.JULIAN_DAY).add(1).multiply(AVE);
final FieldVector3D<T> rotationRate = new FieldVector3D<>(date.getField().getZero(),
date.getField().getZero(),
date.getField().getZero().add(omp));
// set up the transform from parent TOD
return new FieldTransform<>(date,
new FieldRotation<>(FieldVector3D.getPlusK(date.getField()),
gast, RotationConvention.FRAME_TRANSFORM),
rotationRate);
}
/** 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
*/
private Object writeReplace() {
return new DataTransferObject(conventions, eopHistory);
}
/** Internal class used only for serialization. */
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 GTODProvider}.
* @return replacement {@link GTODProvider}
*/
private Object readResolve() {
try {
// retrieve a managed frame
return new GTODProvider(conventions, eopHistory);
} catch (OrekitException oe) {
throw new OrekitInternalError(oe);
}
}
}
}