NadirPointing.java

  1. /* Copyright 2002-2018 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;

  19. import java.util.ArrayList;
  20. import java.util.List;

  22. import org.hipparchus.RealFieldElement;
  23. import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
  24. import org.hipparchus.geometry.euclidean.threed.Vector3D;
  25. import org.orekit.bodies.BodyShape;
  26. import org.orekit.bodies.FieldGeodeticPoint;
  27. import org.orekit.bodies.GeodeticPoint;
  28. import org.orekit.errors.OrekitException;
  29. import org.orekit.frames.FieldTransform;
  30. import org.orekit.frames.Frame;
  31. import org.orekit.frames.Transform;
  32. import org.orekit.time.AbsoluteDate;
  33. import org.orekit.time.FieldAbsoluteDate;
  34. import org.orekit.utils.CartesianDerivativesFilter;
  35. import org.orekit.utils.FieldPVCoordinatesProvider;
  36. import org.orekit.utils.PVCoordinatesProvider;
  37. import org.orekit.utils.TimeStampedFieldPVCoordinates;
  38. import org.orekit.utils.TimeStampedPVCoordinates;

  40. /**
  41.  * This class handles nadir pointing attitude provider.

  43.  * <p>
  44.  * This class represents the attitude provider where the satellite z axis is
  45.  * pointing to the vertical of the ground point under satellite.</p>
  46.  * <p>
  47.  * The object <code>NadirPointing</code> is guaranteed to be immutable.
  48.  * </p>
  49.  * @see     GroundPointing
  50.  * @author V&eacute;ronique Pommier-Maurussane
  51.  */
  52. public class NadirPointing extends GroundPointing {

  54.     /** Serializable UID. */
  55.     private static final long serialVersionUID = 20150529L;

  57.     /** Body shape.  */
  58.     private final BodyShape shape;

  60.     /** Creates new instance.
  61.      * @param inertialFrame frame in which orbital velocities are computed
  62.      * @param shape Body shape
  63.      * @exception OrekitException if the frame specified is not a pseudo-inertial frame
  64.      * @since 7.1
  65.      */
  66.     public NadirPointing(final Frame inertialFrame, final BodyShape shape)
  67.         throws OrekitException {
  68.         // Call constructor of superclass
  69.         super(inertialFrame, shape.getBodyFrame());
  70.         this.shape = shape;
  71.     }

  73.     /** {@inheritDoc} */
  74.     public TimeStampedPVCoordinates getTargetPV(final PVCoordinatesProvider pvProv,
  75.                                                 final AbsoluteDate date, final Frame frame)
  76.         throws OrekitException {

  78.         // transform from specified reference frame to body frame
  79.         final Transform refToBody = frame.getTransformTo(shape.getBodyFrame(), date);

  81.         // sample intersection points in current date neighborhood
  82.         final double h  = 0.01;
  83.         final List<TimeStampedPVCoordinates> sample = new ArrayList<>();
  84.         sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(-2 * h), frame), refToBody.shiftedBy(-2 * h)));
  85.         sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(-h),     frame), refToBody.shiftedBy(-h)));
  86.         sample.add(nadirRef(pvProv.getPVCoordinates(date,                   frame), refToBody));
  87.         sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(+h),     frame), refToBody.shiftedBy(+h)));
  88.         sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(+2 * h), frame), refToBody.shiftedBy(+2 * h)));

  90.         // use interpolation to compute properly the time-derivatives
  91.         return TimeStampedPVCoordinates.interpolate(date, CartesianDerivativesFilter.USE_P, sample);

  93.     }

  95.     /** {@inheritDoc} */
  96.     public <T extends RealFieldElement<T>> TimeStampedFieldPVCoordinates<T> getTargetPV(final FieldPVCoordinatesProvider<T> pvProv,
  97.                                                                                         final FieldAbsoluteDate<T> date,
  98.                                                                                         final Frame frame)
  99.         throws OrekitException {

  101.         // transform from specified reference frame to body frame
  102.         final FieldTransform<T> refToBody = frame.getTransformTo(shape.getBodyFrame(), date);

  104.         // sample intersection points in current date neighborhood
  105.         final double h  = 0.01;
  106.         final List<TimeStampedFieldPVCoordinates<T>> sample = new ArrayList<>();
  107.         sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(-2 * h), frame), refToBody.shiftedBy(-2 * h)));
  108.         sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(-h),     frame), refToBody.shiftedBy(-h)));
  109.         sample.add(nadirRef(pvProv.getPVCoordinates(date,                   frame), refToBody));
  110.         sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(+h),     frame), refToBody.shiftedBy(+h)));
  111.         sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(+2 * h), frame), refToBody.shiftedBy(+2 * h)));

  113.         // use interpolation to compute properly the time-derivatives
  114.         return TimeStampedFieldPVCoordinates.interpolate(date, CartesianDerivativesFilter.USE_P, sample);

  116.     }

  118.     /** Compute ground point in nadir direction, in reference frame.
  119.      * @param scRef spacecraft coordinates in reference frame
  120.      * @param refToBody transform from reference frame to body frame
  121.      * @return intersection point in body frame (only the position is set!)
  122.      * @exception OrekitException if line of sight does not intersect body
  123.      */
  124.     private TimeStampedPVCoordinates nadirRef(final TimeStampedPVCoordinates scRef, final Transform refToBody)
  125.         throws OrekitException {

  127.         final Vector3D satInBodyFrame = refToBody.transformPosition(scRef.getPosition());

  129.         // satellite position in geodetic coordinates
  130.         final GeodeticPoint gpSat = shape.transform(satInBodyFrame, getBodyFrame(), scRef.getDate());

  132.         // nadir position in geodetic coordinates
  133.         final GeodeticPoint gpNadir = new GeodeticPoint(gpSat.getLatitude(), gpSat.getLongitude(), 0.0);

  135.         // nadir point position in body frame
  136.         final Vector3D pNadirBody = shape.transform(gpNadir);

  138.         // nadir point position in reference frame
  139.         final Vector3D pNadirRef = refToBody.getInverse().transformPosition(pNadirBody);

  141.         return new TimeStampedPVCoordinates(scRef.getDate(), pNadirRef, Vector3D.ZERO, Vector3D.ZERO);

  143.     }

  145.     /** Compute ground point in nadir direction, in reference frame.
  146.      * @param scRef spacecraft coordinates in reference frame
  147.      * @param refToBody transform from reference frame to body frame
  148.      * @param <T> type of the field elements
  149.      * @return intersection point in body frame (only the position is set!)
  150.      * @exception OrekitException if line of sight does not intersect body
  151.      * @since 9.0
  152.      */
  153.     private <T extends RealFieldElement<T>> TimeStampedFieldPVCoordinates<T> nadirRef(final TimeStampedFieldPVCoordinates<T> scRef,
  154.                                                                                       final FieldTransform<T> refToBody)
  155.         throws OrekitException {

  157.         final FieldVector3D<T> satInBodyFrame = refToBody.transformPosition(scRef.getPosition());

  159.         // satellite position in geodetic coordinates
  160.         final FieldGeodeticPoint<T> gpSat = shape.transform(satInBodyFrame, getBodyFrame(), scRef.getDate());

  162.         // nadir position in geodetic coordinates
  163.         final FieldGeodeticPoint<T> gpNadir = new FieldGeodeticPoint<>(gpSat.getLatitude(), gpSat.getLongitude(),
  164.                                                                        gpSat.getAltitude().getField().getZero());

  166.         // nadir point position in body frame
  167.         final FieldVector3D<T> pNadirBody = shape.transform(gpNadir);

  169.         // nadir point position in reference frame
  170.         final FieldVector3D<T> pNadirRef = refToBody.getInverse().transformPosition(pNadirBody);

  172.         final FieldVector3D<T> zero = FieldVector3D.getZero(gpSat.getAltitude().getField());
  173.         return new TimeStampedFieldPVCoordinates<>(scRef.getDate(), pNadirRef, zero, zero);

  175.     }

  177. }
Created with JaCoCo 0.7.9.201702052155