VEISProvider.java
/* Copyright 2002-2024 CS GROUP
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* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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package org.orekit.frames;
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.hipparchus.util.MathUtils;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.DateComponents;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.time.TimeScales;
import org.orekit.utils.Constants;
/** Veis 1950 Frame.
* <p>Its parent frame is the {@link GTODProvider} without EOP correction application.
* <p>This frame is mainly provided for consistency with legacy softwares.</p>
* @author Pascal Parraud
*/
class VEISProvider implements TransformProvider {
/** Serializable UID. */
private static final long serialVersionUID = 20130530L;
/** 1st coef for Veis sidereal time computation in radians (100.075542 deg). */
private static final double VST0 = 1.746647708617871;
/** 2nd coef for Veis sidereal time computation in rad/s (0.985612288 deg/s). */
private static final double VST1 = 0.17202179573714597e-1;
/** Veis sidereal time derivative in rad/s. */
private static final double VSTD = 7.292115146705209e-5;
/** Set of time scales to use. */
private final transient TimeScales timeScales;
/** Reference date. */
private final AbsoluteDate vstReference;
/**
* Constructor for the singleton.
*
* @param timeScales to use when computing the transform.
*/
VEISProvider(final TimeScales timeScales) {
this.timeScales = timeScales;
this.vstReference =
new AbsoluteDate(DateComponents.FIFTIES_EPOCH, timeScales.getTAI());
}
/** {@inheritDoc} */
@Override
public Transform getTransform(final AbsoluteDate date) {
// offset from FIFTIES epoch (UT1 scale)
final double dtai = date.durationFrom(vstReference);
final double dutc = timeScales.getUTC().offsetFromTAI(date);
final double dut1 = 0.0; // fixed at 0 since Veis parent is GTOD frame WITHOUT EOP corrections
final double tut1 = dtai + dutc + dut1;
final double ttd = tut1 / Constants.JULIAN_DAY;
final double rdtt = ttd - (int) ttd;
// compute Veis sidereal time, in radians
final double vst = (VST0 + VST1 * ttd + MathUtils.TWO_PI * rdtt) % MathUtils.TWO_PI;
// compute angular rotation of Earth, in rad/s
final Vector3D rotationRate = new Vector3D(-VSTD, Vector3D.PLUS_K);
// set up the transform from parent GTOD
return new Transform(date,
new Rotation(Vector3D.PLUS_K, vst, RotationConvention.VECTOR_OPERATOR),
rotationRate);
}
/** {@inheritDoc} */
@Override
public <T extends CalculusFieldElement<T>> FieldTransform<T> getTransform(final FieldAbsoluteDate<T> date) {
// offset from FIFTIES epoch (UT1 scale)
final T dtai = date.durationFrom(vstReference);
final double dutc = timeScales.getUTC().offsetFromTAI(date.toAbsoluteDate());
final double dut1 = 0.0; // fixed at 0 since Veis parent is GTOD frame WITHOUT EOP corrections
final T tut1 = dtai.add(dutc + dut1);
final T ttd = tut1.divide(Constants.JULIAN_DAY);
final T rdtt = ttd.subtract((int) ttd.getReal());
// compute Veis sidereal time, in radians
final T vst = ttd.multiply(VST1).add(rdtt.multiply(MathUtils.TWO_PI)).add(VST0).remainder(MathUtils.TWO_PI);
// compute angular rotation of Earth, in rad/s
final FieldVector3D<T> rotationRate = new FieldVector3D<>(date.getField().getZero().newInstance(-VSTD),
Vector3D.PLUS_K);
// set up the transform from parent GTOD
return new FieldTransform<>(date,
new FieldRotation<>(FieldVector3D.getPlusK(date.getField()), vst,
RotationConvention.VECTOR_OPERATOR),
rotationRate);
}
}