NadirPointing.java
- /* Copyright 2002-2024 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.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- package org.orekit.attitudes;
- import java.util.ArrayList;
- import java.util.List;
- import org.hipparchus.CalculusFieldElement;
- import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
- import org.hipparchus.geometry.euclidean.threed.Vector3D;
- import org.orekit.bodies.BodyShape;
- import org.orekit.bodies.FieldGeodeticPoint;
- import org.orekit.bodies.GeodeticPoint;
- import org.orekit.frames.FieldStaticTransform;
- import org.orekit.frames.FieldTransform;
- import org.orekit.frames.Frame;
- import org.orekit.frames.StaticTransform;
- import org.orekit.frames.Transform;
- import org.orekit.time.AbsoluteDate;
- import org.orekit.time.FieldAbsoluteDate;
- import org.orekit.time.FieldTimeInterpolator;
- import org.orekit.time.TimeInterpolator;
- import org.orekit.utils.CartesianDerivativesFilter;
- import org.orekit.utils.FieldPVCoordinatesProvider;
- import org.orekit.utils.PVCoordinatesProvider;
- import org.orekit.utils.TimeStampedFieldPVCoordinates;
- import org.orekit.utils.TimeStampedFieldPVCoordinatesHermiteInterpolator;
- import org.orekit.utils.TimeStampedPVCoordinates;
- import org.orekit.utils.TimeStampedPVCoordinatesHermiteInterpolator;
- /**
- * This class handles nadir pointing attitude provider.
- * <p>
- * This class represents the attitude provider where the satellite z axis is
- * pointing to the vertical of the ground point under satellite.</p>
- * <p>
- * The object <code>NadirPointing</code> is guaranteed to be immutable.
- * </p>
- * @see GroundPointing
- * @author Véronique Pommier-Maurussane
- */
- public class NadirPointing extends GroundPointing {
- /** Body shape. */
- private final BodyShape shape;
- /** Creates new instance.
- * @param inertialFrame frame in which orbital velocities are computed
- * @param shape Body shape
- * @since 7.1
- */
- public NadirPointing(final Frame inertialFrame, final BodyShape shape) {
- // Call constructor of superclass
- super(inertialFrame, shape.getBodyFrame());
- this.shape = shape;
- }
- /** {@inheritDoc} */
- public TimeStampedPVCoordinates getTargetPV(final PVCoordinatesProvider pvProv,
- final AbsoluteDate date, final Frame frame) {
- // transform from specified reference frame to body frame
- final Transform refToBody = frame.getTransformTo(shape.getBodyFrame(), date);
- // sample intersection points in current date neighborhood
- final double h = 0.01;
- final List<TimeStampedPVCoordinates> sample = new ArrayList<>();
- sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(-2 * h), frame), refToBody.staticShiftedBy(-2 * h)));
- sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(-h), frame), refToBody.staticShiftedBy(-h)));
- sample.add(nadirRef(pvProv.getPVCoordinates(date, frame), refToBody));
- sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(+h), frame), refToBody.staticShiftedBy(+h)));
- sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(+2 * h), frame), refToBody.staticShiftedBy(+2 * h)));
- // create interpolator
- final TimeInterpolator<TimeStampedPVCoordinates> interpolator =
- new TimeStampedPVCoordinatesHermiteInterpolator(sample.size(), CartesianDerivativesFilter.USE_P);
- // use interpolation to compute properly the time-derivatives
- return interpolator.interpolate(date, sample);
- }
- /** {@inheritDoc} */
- public <T extends CalculusFieldElement<T>> TimeStampedFieldPVCoordinates<T> getTargetPV(final FieldPVCoordinatesProvider<T> pvProv,
- final FieldAbsoluteDate<T> date,
- final Frame frame) {
- // zero
- final T zero = date.getField().getZero();
- // transform from specified reference frame to body frame
- final FieldTransform<T> refToBody = frame.getTransformTo(shape.getBodyFrame(), date);
- // sample intersection points in current date neighborhood
- final double h = 0.01;
- final List<TimeStampedFieldPVCoordinates<T>> sample = new ArrayList<>();
- sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(-2 * h), frame), refToBody.staticShiftedBy(zero.add(-2 * h))));
- sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(-h), frame), refToBody.staticShiftedBy(zero.add(-h))));
- sample.add(nadirRef(pvProv.getPVCoordinates(date, frame), refToBody));
- sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(+h), frame), refToBody.staticShiftedBy(zero.add(+h))));
- sample.add(nadirRef(pvProv.getPVCoordinates(date.shiftedBy(+2 * h), frame), refToBody.staticShiftedBy(zero.add(+2 * h))));
- // create interpolator
- final FieldTimeInterpolator<TimeStampedFieldPVCoordinates<T>, T> interpolator =
- new TimeStampedFieldPVCoordinatesHermiteInterpolator<>(sample.size(), CartesianDerivativesFilter.USE_P);
- // use interpolation to compute properly the time-derivatives
- return interpolator.interpolate(date, sample);
- }
- /** Compute ground point in nadir direction, in reference frame.
- * @param scRef spacecraft coordinates in reference frame
- * @param refToBody transform from reference frame to body frame
- * @return intersection point in body frame (only the position is set!)
- */
- private TimeStampedPVCoordinates nadirRef(final TimeStampedPVCoordinates scRef,
- final StaticTransform refToBody) {
- final Vector3D satInBodyFrame = refToBody.transformPosition(scRef.getPosition());
- // satellite position in geodetic coordinates
- final GeodeticPoint gpSat = shape.transform(satInBodyFrame, getBodyFrame(), scRef.getDate());
- // nadir position in geodetic coordinates
- final GeodeticPoint gpNadir = new GeodeticPoint(gpSat.getLatitude(), gpSat.getLongitude(), 0.0);
- // nadir point position in body frame
- final Vector3D pNadirBody = shape.transform(gpNadir);
- // nadir point position in reference frame
- final Vector3D pNadirRef = refToBody.getInverse().transformPosition(pNadirBody);
- return new TimeStampedPVCoordinates(scRef.getDate(), pNadirRef, Vector3D.ZERO, Vector3D.ZERO);
- }
- /** Compute ground point in nadir direction, in reference frame.
- * @param scRef spacecraft coordinates in reference frame
- * @param refToBody transform from reference frame to body frame
- * @param <T> type of the field elements
- * @return intersection point in body frame (only the position is set!)
- * @since 9.0
- */
- private <T extends CalculusFieldElement<T>> TimeStampedFieldPVCoordinates<T> nadirRef(final TimeStampedFieldPVCoordinates<T> scRef,
- final FieldStaticTransform<T> refToBody) {
- final FieldVector3D<T> satInBodyFrame = refToBody.transformPosition(scRef.getPosition());
- // satellite position in geodetic coordinates
- final FieldGeodeticPoint<T> gpSat = shape.transform(satInBodyFrame, getBodyFrame(), scRef.getDate());
- // nadir position in geodetic coordinates
- final FieldGeodeticPoint<T> gpNadir = new FieldGeodeticPoint<>(gpSat.getLatitude(), gpSat.getLongitude(),
- gpSat.getAltitude().getField().getZero());
- // nadir point position in body frame
- final FieldVector3D<T> pNadirBody = shape.transform(gpNadir);
- // nadir point position in reference frame
- final FieldVector3D<T> pNadirRef = refToBody.getInverse().transformPosition(pNadirBody);
- final FieldVector3D<T> zero = FieldVector3D.getZero(gpSat.getAltitude().getField());
- return new TimeStampedFieldPVCoordinates<>(scRef.getDate(), pNadirRef, zero, zero);
- }
- }