FixedRate.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.attitudes;

  18. import org.hipparchus.Field;
  19. import org.hipparchus.RealFieldElement;
  20. import org.orekit.frames.Frame;
  21. import org.orekit.time.AbsoluteDate;
  22. import org.orekit.time.FieldAbsoluteDate;
  23. import org.orekit.utils.FieldPVCoordinatesProvider;
  24. import org.orekit.utils.PVCoordinatesProvider;


  25. /**
  26.  * This class handles a simple attitude provider at constant rate around a fixed axis.
  27.  * <p>This attitude provider is a simple linear extrapolation from an initial
  28.  * orientation, a rotation axis and a rotation rate. All this elements can be
  29.  * specified as a simple {@link Attitude reference attitude}.</p>
  30.  * <p>Instances of this class are guaranteed to be immutable.</p>
  31.  * @author Luc Maisonobe
  32.  */
  33. public class FixedRate implements AttitudeProvider {

  34.     /** Reference attitude.  */
  35.     private final Attitude referenceAttitude;

  36.     /** Creates a new instance.
  37.      * @param referenceAttitude attitude at reference date
  38.      */
  39.     public FixedRate(final Attitude referenceAttitude) {
  40.         this.referenceAttitude = referenceAttitude;
  41.     }

  42.     /** {@inheritDoc} */
  43.     public Attitude getAttitude(final PVCoordinatesProvider pvProv,
  44.                                 final AbsoluteDate date, final Frame frame) {
  45.         final double timeShift = date.durationFrom(referenceAttitude.getDate());
  46.         final Attitude shifted = referenceAttitude.shiftedBy(timeShift);
  47.         return shifted.withReferenceFrame(frame);
  48.     }

  49.     /** {@inheritDoc} */
  50.     public <T extends RealFieldElement<T>> FieldAttitude<T> getAttitude(final FieldPVCoordinatesProvider<T> pvProv,
  51.                                                                         final FieldAbsoluteDate<T> date,
  52.                                                                         final Frame frame) {
  53.         final Field<T> field = date.getField();
  54.         final T timeShift = date.durationFrom(referenceAttitude.getDate());
  55.         final FieldAttitude<T> shifted = new FieldAttitude<>(field, referenceAttitude).shiftedBy(timeShift);
  56.         return shifted.withReferenceFrame(frame);
  57.     }

  58.     /** Get the reference attitude.
  59.      * @return reference attitude
  60.      */
  61.     public Attitude getReferenceAttitude() {
  62.         return referenceAttitude;
  63.     }

  64. }