GTODProvider.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.frames;
- import java.io.Serializable;
- import org.hipparchus.CalculusFieldElement;
- 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.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.TimeScale;
- import org.orekit.time.TimeScales;
- 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)
- * @param timeScales set of time scales to use.
- * @since 10.1
- */
- protected GTODProvider(final IERSConventions conventions,
- final EOPHistory eopHistory,
- final TimeScales timeScales) {
- final TimeScale ut1 = eopHistory == null ?
- timeScales.getUTC() : // UT1 wihthout EOP is UTC
- timeScales.getUT1(eopHistory.getConventions(), eopHistory.isSimpleEop());
- this.conventions = conventions;
- this.eopHistory = eopHistory;
- this.gastFunction = conventions.getGASTFunction(ut1, eopHistory, timeScales);
- }
- /**
- * Private constructor.
- *
- * @param conventions IERS conventions to use
- * @param eopHistory EOP history (may be null)
- * @param gastFunction GAST function
- */
- private GTODProvider(final IERSConventions conventions,
- final EOPHistory eopHistory,
- final TimeScalarFunction gastFunction) {
- this.conventions = conventions;
- this.eopHistory = eopHistory;
- this.gastFunction = gastFunction;
- }
- /** {@inheritDoc} */
- @Override
- public EOPHistory getEOPHistory() {
- return eopHistory;
- }
- /** {@inheritDoc} */
- @Override
- public GTODProvider getNonInterpolatingProvider() {
- return new GTODProvider(conventions, eopHistory.getNonInterpolatingEOPHistory(),
- gastFunction);
- }
- /** {@inheritDoc} */
- @Override
- public Transform getTransform(final AbsoluteDate date) {
- // 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 StaticTransform getStaticTransform(final AbsoluteDate date) {
- // compute Greenwich apparent sidereal time, in radians
- final double gast = gastFunction.value(date);
- // set up the transform from parent TOD
- return StaticTransform.of(
- date,
- new Rotation(Vector3D.PLUS_K, gast, RotationConvention.FRAME_TRANSFORM));
- }
- /** {@inheritDoc} */
- @Override
- public <T extends CalculusFieldElement<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
- */
- @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 GTODProvider}.
- * @return replacement {@link GTODProvider}
- */
- private Object readResolve() {
- try {
- // retrieve a managed frame
- return new GTODProvider(conventions, eopHistory,
- DataContext.getDefault().getTimeScales());
- } catch (OrekitException oe) {
- throw new OrekitInternalError(oe);
- }
- }
- }
- }