- /* Copyright 2002-2016 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.apache.commons.math3.analysis.differentiation.DerivativeStructure;
- import org.apache.commons.math3.geometry.euclidean.threed.Rotation;
- import org.apache.commons.math3.geometry.euclidean.threed.RotationConvention;
- import org.apache.commons.math3.geometry.euclidean.threed.Vector3D;
- import org.orekit.errors.OrekitException;
- import org.orekit.errors.OrekitInternalError;
- import org.orekit.time.AbsoluteDate;
- import org.orekit.time.TimeFunction;
- 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 TimeFunction<DerivativeStructure> 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());
- }
- /** Get the transform from TOD at specified date.
- * <p>The update considers the Earth rotation from IERS data.</p>
- * @param date new value of the date
- * @return transform at the specified date
- * @exception OrekitException if the nutation model data embedded in the
- * library cannot be read
- */
- public Transform getTransform(final AbsoluteDate date) throws OrekitException {
- // compute Greenwich apparent sidereal time, in radians
- final double gast = gastFunction.value(date).getValue();
- // 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);
- }
- /** 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);
- }
- }
- }
- }