AbstractParametricAcceleration.java
- /* Copyright 2002-2020 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.forces;
- import java.util.stream.Stream;
- import org.hipparchus.Field;
- import org.hipparchus.RealFieldElement;
- import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
- import org.hipparchus.geometry.euclidean.threed.Vector3D;
- import org.orekit.attitudes.Attitude;
- import org.orekit.attitudes.AttitudeProvider;
- import org.orekit.attitudes.FieldAttitude;
- import org.orekit.propagation.FieldSpacecraftState;
- import org.orekit.propagation.SpacecraftState;
- import org.orekit.propagation.events.EventDetector;
- import org.orekit.propagation.events.FieldEventDetector;
- /** This class implements a parametric acceleration.
- * <p>Parametric accelerations are intended to model lesser-known
- * forces, estimating a few defining parameters from a parametric
- * function using orbit determination. Typical parametric functions
- * are polynomial (often limited to a constant term) and harmonic
- * (often with either orbital period or half orbital period).</p>
- * <p>An important operational example is the infamous GPS Y-bias,
- * which is thought to be related to a radiator thermal radiation.
- * Other examples could be to model leaks that produce roughly constant
- * trust in some spacecraft-related direction.</p>
- * <p>The acceleration direction is considered constant in either:
- * </p>
- * <ul>
- * <li>inertial frame</li>
- * <li>spacecraft frame</li>
- * <li>a dedicated attitude frame overriding spacecraft attitude
- * (this could for example be used to model solar arrays orientation
- * if the force is related to solar arrays)</li>
- * </ul>
- * <p>
- * If the direction of the acceleration is unknown, then three instances
- * of this class should be used, one along the X axis, one along the Y
- * axis and one along the Z axis and their parameters estimated as usual.
- * </p>
- * @since 9.0
- * @author Luc Maisonobe
- */
- public abstract class AbstractParametricAcceleration extends AbstractForceModel {
- /** Direction of the acceleration in defining frame. */
- private final Vector3D direction;
- /** Flag for inertial acceleration direction. */
- private final boolean isInertial;
- /** The attitude to override, if set. */
- private final AttitudeProvider attitudeOverride;
- /** Simple constructor.
- * @param direction acceleration direction in overridden spacecraft frame
- * @param isInertial if true, direction is defined in the same inertial
- * frame used for propagation (i.e. {@link SpacecraftState#getFrame()}),
- * otherwise direction is defined in spacecraft frame (i.e. using the
- * propagation {@link
- * org.orekit.propagation.Propagator#setAttitudeProvider(AttitudeProvider)
- * attitude law})
- * @param attitudeOverride provider for attitude used to compute acceleration
- * direction
- */
- protected AbstractParametricAcceleration(final Vector3D direction, final boolean isInertial,
- final AttitudeProvider attitudeOverride) {
- this.direction = direction;
- this.isInertial = isInertial;
- this.attitudeOverride = attitudeOverride;
- }
- /** Check if direction is inertial.
- * @return true if direction is inertial
- */
- protected boolean isInertial() {
- return isInertial;
- }
- /** Compute the signed amplitude of the acceleration.
- * <p>
- * The acceleration is the direction multiplied by the signed amplitude. So if
- * signed amplitude is negative, the acceleratin is towards the opposite of the
- * direction specified at construction.
- * </p>
- * @param state current state information: date, kinematics, attitude
- * @param parameters values of the force model parameters
- * @return norm of the acceleration
- */
- protected abstract double signedAmplitude(SpacecraftState state, double[] parameters);
- /** Compute the signed amplitude of the acceleration.
- * <p>
- * The acceleration is the direction multiplied by the signed amplitude. So if
- * signed amplitude is negative, the acceleratin is towards the opposite of the
- * direction specified at construction.
- * </p>
- * @param state current state information: date, kinematics, attitude
- * @param parameters values of the force model parameters
- * @param <T> type of the elements
- * @return norm of the acceleration
- */
- protected abstract <T extends RealFieldElement<T>> T signedAmplitude(FieldSpacecraftState<T> state, T[] parameters);
- /** {@inheritDoc} */
- @Override
- public Vector3D acceleration(final SpacecraftState state, final double[] parameters) {
- final Vector3D inertialDirection;
- if (isInertial) {
- // the acceleration direction is already defined in the inertial frame
- inertialDirection = direction;
- } else {
- final Attitude attitude;
- if (attitudeOverride == null) {
- // the acceleration direction is defined in spacecraft frame as set by the propagator
- attitude = state.getAttitude();
- } else {
- // the acceleration direction is defined in a dedicated frame
- attitude = attitudeOverride.getAttitude(state.getOrbit(), state.getDate(), state.getFrame());
- }
- inertialDirection = attitude.getRotation().applyInverseTo(direction);
- }
- return new Vector3D(signedAmplitude(state, parameters), inertialDirection);
- }
- /** {@inheritDoc} */
- @Override
- public <T extends RealFieldElement<T>> FieldVector3D<T> acceleration(final FieldSpacecraftState<T> state,
- final T[] parameters) {
- final FieldVector3D<T> inertialDirection;
- if (isInertial) {
- // the acceleration direction is already defined in the inertial frame
- inertialDirection = new FieldVector3D<>(state.getDate().getField(), direction);
- } else {
- final FieldAttitude<T> attitude;
- if (attitudeOverride == null) {
- // the acceleration direction is defined in spacecraft frame as set by the propagator
- attitude = state.getAttitude();
- } else {
- // the acceleration direction is defined in a dedicated frame
- attitude = attitudeOverride.getAttitude(state.getOrbit(), state.getDate(), state.getFrame());
- }
- inertialDirection = attitude.getRotation().applyInverseTo(direction);
- }
- return new FieldVector3D<>(signedAmplitude(state, parameters), inertialDirection);
- }
- /** {@inheritDoc} */
- @Override
- public Stream<EventDetector> getEventsDetectors() {
- return Stream.empty();
- }
- /** {@inheritDoc} */
- @Override
- public <T extends RealFieldElement<T>> Stream<FieldEventDetector<T>> getFieldEventsDetectors(final Field<T> field) {
- return Stream.empty();
- }
- }