/* 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 java.util.HashMap;
import java.util.Map;
import org.hipparchus.Field;
import org.hipparchus.RealFieldElement;
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.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.TimeVectorFunction;
import org.orekit.utils.IERSConventions;
/** Mean Equator, Mean Equinox Frame.
* <p>This frame handles precession effects according to to selected IERS conventions.</p>
* <p>Its parent frame is the GCRF frame.
* <p>It is sometimes called Mean of Date (MoD) frame.
* @author Pascal Parraud
*/
class MODProvider implements TransformProvider {
/** Serializable UID. */
private static final long serialVersionUID = 20130920L;
/** Conventions. */
private final IERSConventions conventions;
/** Function computing the precession angles. */
private final transient TimeVectorFunction precessionFunction;
/** Constant rotation between ecliptic and equator poles at J2000.0. */
private final Rotation r4;
/** Constant rotations between ecliptic and equator poles at J2000.0. */
private final transient Map<Field<? extends RealFieldElement<?>>, FieldRotation<? extends RealFieldElement<?>>> fieldR4;
/** Simple constructor.
* @param conventions IERS conventions to apply
* @exception OrekitException if IERS conventions tables cannot be read
*/
MODProvider(final IERSConventions conventions) throws OrekitException {
this.conventions = conventions;
this.precessionFunction = conventions.getPrecessionFunction();
final TimeScalarFunction epsilonAFunction = conventions.getMeanObliquityFunction();
final AbsoluteDate date0 = conventions.getNutationReferenceEpoch();
final double epsilon0 = epsilonAFunction.value(date0);
r4 = new Rotation(Vector3D.PLUS_I, epsilon0, RotationConvention.FRAME_TRANSFORM);
fieldR4 = new HashMap<>();
}
/** {@inheritDoc} */
@Override
public Transform getTransform(final AbsoluteDate date) {
// compute the precession angles phiA, omegaA, chiA
final double[] angles = precessionFunction.value(date);
// complete precession
final Rotation precession = r4.compose(new Rotation(RotationOrder.ZXZ, RotationConvention.FRAME_TRANSFORM,
-angles[0], -angles[1], angles[2]),
RotationConvention.FRAME_TRANSFORM);
// set up the transform from parent GCRF
return new Transform(date, precession);
}
/** {@inheritDoc} */
@Override
public <T extends RealFieldElement<T>> FieldTransform<T> getTransform(final FieldAbsoluteDate<T> date)
throws OrekitException {
// compute the precession angles phiA, omegaA, chiA
final T[] angles = precessionFunction.value(date);
@SuppressWarnings("unchecked")
FieldRotation<T> fR4 = (FieldRotation<T>) fieldR4.get(date.getField());
if (fR4 == null) {
fR4 = new FieldRotation<>(date.getField(), r4);
fieldR4.put(date.getField(), fR4);
}
// complete precession
final FieldRotation<T> precession = fR4.compose(new FieldRotation<>(RotationOrder.ZXZ, RotationConvention.FRAME_TRANSFORM,
angles[0].negate(),
angles[1].negate(),
angles[2]),
RotationConvention.FRAME_TRANSFORM);
// set up the transform from parent GCRF
return new FieldTransform<>(date, precession);
}
/** 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);
}
/** 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;
/** Simple constructor.
* @param conventions IERSConventions conventions
*/
DataTransferObject(final IERSConventions conventions) {
this.conventions = conventions;
}
/** Replace the deserialized data transfer object with a {@link MODProvider}.
* @return replacement {@link MODProvider}
*/
private Object readResolve() {
try {
// retrieve a managed frame
return new MODProvider(conventions);
} catch (OrekitException oe) {
throw new OrekitInternalError(oe);
}
}
}
}