EME2000Provider.java
/* Copyright 2002-2020 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.
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package org.orekit.frames;
import org.hipparchus.geometry.euclidean.threed.Rotation;
import org.hipparchus.geometry.euclidean.threed.RotationConvention;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.hipparchus.util.FastMath;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.Constants;
/** EME2000 frame : mean equator at J2000.0.
* <p>This frame was the standard inertial reference prior to GCRF. It was defined
* using Lieske precession-nutation model for Earth. This frame has been superseded
* by GCRF which is implicitly defined from a few hundred quasars coordinates.
* <p>The transformation between GCRF and EME2000 is a constant rotation bias.</p>
* @author Luc Maisonobe
*/
class EME2000Provider extends FixedTransformProvider {
/** Serializable UID. */
private static final long serialVersionUID = -6134137187835219727L;
/** Obliquity of the ecliptic. */
private static final double EPSILON_0 = 84381.448 * Constants.ARC_SECONDS_TO_RADIANS;
/** Bias in longitude. */
private static final double D_PSI_B = -0.041775 * Constants.ARC_SECONDS_TO_RADIANS;
/** Bias in obliquity. */
private static final double D_EPSILON_B = -0.0068192 * Constants.ARC_SECONDS_TO_RADIANS;
/** Right Ascension of the 2000 equinox in ICRS frame. */
private static final double ALPHA_0 = -0.0146 * Constants.ARC_SECONDS_TO_RADIANS;
/** Simple constructor.
*/
protected EME2000Provider() {
// build the bias transform
super(new Transform(AbsoluteDate.ARBITRARY_EPOCH,
new Rotation(Vector3D.PLUS_I, D_EPSILON_B, RotationConvention.VECTOR_OPERATOR).
compose(new Rotation(Vector3D.PLUS_J, -D_PSI_B * FastMath.sin(EPSILON_0), RotationConvention.VECTOR_OPERATOR).
compose(new Rotation(Vector3D.PLUS_K, -ALPHA_0, RotationConvention.VECTOR_OPERATOR), RotationConvention.VECTOR_OPERATOR),
RotationConvention.VECTOR_OPERATOR)));
}
}