VEISProvider.java

  1. /* Copyright 2002-2019 CS Systèmes d'Information
  2.  * Licensed to CS Systèmes d'Information (CS) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * CS licenses this file to You under the Apache License, Version 2.0
  6.  * (the "License"); you may not use this file except in compliance with
  7.  * the License.  You may obtain a copy of the License at
  8.  *
  9.  *   http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  17. package org.orekit.frames;

  18. import org.hipparchus.RealFieldElement;
  19. import org.hipparchus.geometry.euclidean.threed.FieldRotation;
  20. import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
  21. import org.hipparchus.geometry.euclidean.threed.Rotation;
  22. import org.hipparchus.geometry.euclidean.threed.RotationConvention;
  23. import org.hipparchus.geometry.euclidean.threed.Vector3D;
  24. import org.hipparchus.util.MathUtils;
  25. import org.orekit.time.AbsoluteDate;
  26. import org.orekit.time.DateComponents;
  27. import org.orekit.time.FieldAbsoluteDate;
  28. import org.orekit.time.TimeScalesFactory;
  29. import org.orekit.utils.Constants;

  30. /** Veis 1950 Frame.
  31.  * <p>Its parent frame is the {@link GTODProvider} without EOP correction application.
  32.  * <p>This frame is mainly provided for consistency with legacy softwares.</p>
  33.  * @author Pascal Parraud
  34.  */
  35. class VEISProvider implements TransformProvider {

  36.     /** Serializable UID. */
  37.     private static final long serialVersionUID = 20130530L;

  38.     /** Reference date. */
  39.     private static AbsoluteDate VST_REFERENCE =
  40.         new AbsoluteDate(DateComponents.FIFTIES_EPOCH, TimeScalesFactory.getTAI());

  41.     /** 1st coef for Veis sidereal time computation in radians (100.075542 deg). */
  42.     private static final double VST0 = 1.746647708617871;

  43.     /** 2nd coef for Veis sidereal time computation in rad/s (0.985612288 deg/s). */
  44.     private static final double VST1 = 0.17202179573714597e-1;

  45.     /** Veis sidereal time derivative in rad/s. */
  46.     private static final double VSTD = 7.292115146705209e-5;

  47.     /** Constructor for the singleton.
  48.      */
  49.     VEISProvider() {
  50.     }

  51.     /** {@inheritDoc} */
  52.     @Override
  53.     public Transform getTransform(final AbsoluteDate date) {

  54.         // offset from FIFTIES epoch (UT1 scale)
  55.         final double dtai = date.durationFrom(VST_REFERENCE);
  56.         final double dutc = TimeScalesFactory.getUTC().offsetFromTAI(date);
  57.         final double dut1 = 0.0; // fixed at 0 since Veis parent is GTOD frame WITHOUT EOP corrections

  58.         final double tut1 = dtai + dutc + dut1;
  59.         final double ttd  = tut1 / Constants.JULIAN_DAY;
  60.         final double rdtt = ttd - (int) ttd;

  61.         // compute Veis sidereal time, in radians
  62.         final double vst = (VST0 + VST1 * ttd + MathUtils.TWO_PI * rdtt) % MathUtils.TWO_PI;

  63.         // compute angular rotation of Earth, in rad/s
  64.         final Vector3D rotationRate = new Vector3D(-VSTD, Vector3D.PLUS_K);

  65.         // set up the transform from parent GTOD
  66.         return new Transform(date,
  67.                              new Rotation(Vector3D.PLUS_K, vst, RotationConvention.VECTOR_OPERATOR),
  68.                              rotationRate);

  69.     }

  70.     /** {@inheritDoc} */
  71.     @Override
  72.     public <T extends RealFieldElement<T>> FieldTransform<T> getTransform(final FieldAbsoluteDate<T> date) {

  73.         // offset from FIFTIES epoch (UT1 scale)
  74.         final T dtai = date.durationFrom(VST_REFERENCE);
  75.         final double dutc = TimeScalesFactory.getUTC().offsetFromTAI(date.toAbsoluteDate());
  76.         final double dut1 = 0.0; // fixed at 0 since Veis parent is GTOD frame WITHOUT EOP corrections

  77.         final T tut1 = dtai.add(dutc + dut1);
  78.         final T ttd  = tut1.divide(Constants.JULIAN_DAY);
  79.         final T rdtt = ttd.subtract((int) ttd.getReal());

  80.         // compute Veis sidereal time, in radians
  81.         final T vst = ttd.multiply(VST1).add(rdtt.multiply(MathUtils.TWO_PI)).add(VST0).remainder(MathUtils.TWO_PI);

  82.         // compute angular rotation of Earth, in rad/s
  83.         final FieldVector3D<T> rotationRate = new FieldVector3D<>(date.getField().getZero().add(-VSTD),
  84.                                                                   Vector3D.PLUS_K);

  85.         // set up the transform from parent GTOD
  86.         return new FieldTransform<>(date,
  87.                                     new FieldRotation<>(FieldVector3D.getPlusK(date.getField()), vst,
  88.                                                         RotationConvention.VECTOR_OPERATOR),
  89.                                     rotationRate);

  90.     }

  91. }