TimeSpanDragForce.java
- /* Copyright 2002-2022 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.drag;
- import java.util.ArrayList;
- import java.util.List;
- import java.util.NavigableSet;
- import java.util.stream.Stream;
- import org.hipparchus.CalculusFieldElement;
- import org.hipparchus.Field;
- import org.hipparchus.analysis.differentiation.DerivativeStructure;
- import org.hipparchus.analysis.differentiation.Gradient;
- import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
- import org.hipparchus.geometry.euclidean.threed.Vector3D;
- import org.hipparchus.ode.events.Action;
- import org.hipparchus.util.MathArrays;
- import org.orekit.annotation.DefaultDataContext;
- import org.orekit.frames.Frame;
- import org.orekit.models.earth.atmosphere.Atmosphere;
- import org.orekit.propagation.FieldSpacecraftState;
- import org.orekit.propagation.SpacecraftState;
- import org.orekit.propagation.events.DateDetector;
- import org.orekit.propagation.events.EventDetector;
- import org.orekit.propagation.events.FieldDateDetector;
- import org.orekit.propagation.events.FieldEventDetector;
- import org.orekit.time.AbsoluteDate;
- import org.orekit.time.FieldAbsoluteDate;
- import org.orekit.time.TimeScale;
- import org.orekit.time.TimeScalesFactory;
- import org.orekit.utils.ParameterDriver;
- import org.orekit.utils.TimeSpanMap;
- import org.orekit.utils.TimeSpanMap.Span;
- import org.orekit.utils.TimeSpanMap.Transition;
- /** Time span atmospheric drag force model.
- * <p>
- * This class is closely related to {@link org.orekit.forces.drag.DragForce DragForce} class.<br>
- * The difference is that it has a {@link TimeSpanMap} of {@link DragSensitive} objects as attribute
- * instead of a single {@link DragSensitive} object. <br>
- * The idea behind this model is to allow the user to design a drag force model that can see its physical parameters
- * (drag coefficient and lift ratio) change with time, at dates chosen by the user. <br>
- * </p>
- * <p>
- * This is a behavior that can be sought in operational orbit determination.<br>
- * Indeed the solar activity has a strong influence on the local atmospheric density, and thus on the drag force effect.<br>
- * Solar activity is a physical phenomenon that is difficult to model and predict. <br>
- * The errors induced by this incomplete modeling can be estimated through the drag coefficients.<br>
- * Being able to define and estimate drag coefficients depending on user-chosen dates in a piecewise fashion allows for
- * a better modeling of solar activity uncertainties.
- * </p>
- * <p>
- * A typical operational use case is to have a daily solar activity with three-hourly magnetic indexes provided by an
- * international organization (NOAA for example).<br>
- * Given this input, a user can define a piecewise drag force model with daily or three-hourly drag coefficients.<br>
- * Each timed coefficient will absorb a part of the uncertainties in the solar activity and will allow for a more accurate
- * orbit determination
- * </p>
- * <b>Usage</b>:<ul>
- * <li><u>Construction</u>: constructor takes an atmospheric model and a DragSensitive model.<br>
- * This last model will be your initial DragSensitive model and it will be initially valid for the whole time line.<br>
- * The real validity of this first entry will be truncated as other DragSensitive models are added.
- * <li><u>Time spans</u>: DragSensitive models are added using methods {@link #addDragSensitiveValidAfter(DragSensitive, AbsoluteDate)}
- * or {@link #addDragSensitiveValidBefore(DragSensitive, AbsoluteDate)}.<br>
- * Recommendations are the same than the ones in {@link TimeSpanMap}, meaning: <ul>
- * <li>As an entry is added, it truncates the validity of the neighboring entries already present in the map;
- * <li><b>The transition dates should be entered only once</b>. Repeating a transition date will lead to unexpected result and is not supported;
- * <li>It is advised to order your DragSensitive models chronologically when adding them to avoid any confusion.
- * </ul>
- * <li><u>Naming the parameter drivers</u>: It is strongly advised to give a custom name to the {@link ParameterDriver}(s)
- * of each DragSensitive model that is added to the object. This will allow you keeping track of the evolution of your models.<br>
- * Different names are mandatory to differentiate the different drivers.<br>
- * If you do not specify a name, a default name will be chosen. Example for the drag coefficient:<ul>
- * <li>Initial DragSensitive model: the driver's default name is "{@link DragSensitive#DRAG_COEFFICIENT}";
- * <li>Using {@link #addDragSensitiveValidAfter(DragSensitive, AbsoluteDate)}: the driver's default name is
- * "{@link DragSensitive#DRAG_COEFFICIENT} + {@link #DATE_AFTER} + date.toString()"
- * <li>Using {@link #addDragSensitiveValidBefore(DragSensitive, AbsoluteDate)}: the driver's default name is
- * "{@link DragSensitive#DRAG_COEFFICIENT} + {@link #DATE_BEFORE} + date.toString()"
- * </ul>
- * </ul>
- * <b>Example following previous recommendations</b>:<ul>
- * <li>Given:
- * <ul>
- * <li><code>atmosphere</code>: an {@link Atmosphere atmospheric model};
- * <li><code>isotropicDrag0, 1 and 2</code>: three {@link org.orekit.forces.drag.IsotropicDrag IsotropicDrag} models;
- * <li><code>date</code>: an {@link AbsoluteDate}.
- * </ul>
- * <li>Name the drivers:<br>
- * <code>isotropicDrag0.getDragParametersDrivers()[0].setName = "Cd0";</code><br>
- * <code>isotropicDrag1.getDragParametersDrivers()[0].setName = "Cd1";</code><br>
- * <code>isotropicDrag2.getDragParametersDrivers()[0].setName = "Cd2";</code><br>
- * <li>Initialize the model: <br>
- * <code>TimeSpanDragForce force = new TimeSpanDragForce(atmosphere, isotropicDrag0);</code>
- * <li>Set the second and third model one Julian day apart each:<br>
- * <code>force.addDragSensitiveValidAfter(isotropicDrag1, date.shiftedBy(Constants.JULIAN_DAY));</code><br>
- * <code>force.addDragSensitiveValidAfter(isotropicDrag2, date.shiftedBy(2 * Constants.JULIAN_DAY));</code><br>
- * <li>With this, your model will have the following properties:
- * <ul>
- * <li>t in ]-∞, date + 1 day [ / Cd = Cd0
- * <li>t in [date + 1 day, date + 2days [ / Cd = Cd1
- * <li>t in [date + 2 days, +∞ [ / Cd = Cd2
- * </ul>
- * </ul>
- * <p>
- * <b>Warning</b>:<br> The TimeSpanDragForce model is versatile and you could end up with non-physical modeling.<br>
- * For example you could add 2 {@link org.orekit.forces.drag.IsotropicDrag IsotropicDrag} models with different areas,
- * or one {@link org.orekit.forces.drag.IsotropicDrag IsotropicDrag} model and then one
- * {@link org.orekit.forces.BoxAndSolarArraySpacecraft BoxAndSolarArraySpacecraft} model.<br>
- * It is up to you to ensure that your models are consistent with each other, Orekit will not perform any check for that.
- * </p>
- * @author Maxime Journot
- * @since 10.2
- */
- public class TimeSpanDragForce extends AbstractDragForceModel {
- /** Prefix for dates before in the parameter drivers' name. */
- public static final String DATE_BEFORE = " - Before ";
- /** Prefix for dates after in the parameter drivers' name. */
- public static final String DATE_AFTER = " - After ";
- /** Atmospheric model. */
- private final Atmosphere atmosphere;
- /** TimeSpanMap of DragSensitive objects. */
- private final TimeSpanMap<DragSensitive> dragSensitiveTimeSpanMap;
- /** Time scale used for the default names of the drag parameter drivers. */
- private final TimeScale timeScale;
- /** Constructor with default UTC time scale for the default names of the drag parameter drivers.
- * @param atmosphere atmospheric model
- * @param spacecraft Time scale used for the default names of the drag parameter drivers
- */
- @DefaultDataContext
- public TimeSpanDragForce(final Atmosphere atmosphere,
- final DragSensitive spacecraft) {
- super(atmosphere);
- this.atmosphere = atmosphere;
- this.dragSensitiveTimeSpanMap = new TimeSpanMap<>(spacecraft);
- this.timeScale = TimeScalesFactory.getUTC();
- }
- /** Constructor.
- * @param atmosphere atmospheric model
- * @param spacecraft the initial object physical and geometric information
- * @param timeScale Time scale used for the default names of the drag parameter drivers
- */
- public TimeSpanDragForce(final Atmosphere atmosphere,
- final DragSensitive spacecraft,
- final TimeScale timeScale) {
- super(atmosphere);
- this.atmosphere = atmosphere;
- this.dragSensitiveTimeSpanMap = new TimeSpanMap<>(spacecraft);
- this.timeScale = timeScale;
- }
- /** Add a DragSensitive entry valid before a limit date.<br>
- * Using <code>addDragSensitiveValidBefore(entry, t)</code> will make <code>entry</code>
- * valid in ]-∞, t[ (note the open bracket).
- * @param dragSensitive DragSensitive entry
- * @param latestValidityDate date before which the entry is valid
- * (must be different from <b>all</b> dates already used for transitions)
- */
- public void addDragSensitiveValidBefore(final DragSensitive dragSensitive, final AbsoluteDate latestValidityDate) {
- dragSensitiveTimeSpanMap.addValidBefore(changeDragParameterDriversNames(dragSensitive,
- latestValidityDate,
- DATE_BEFORE),
- latestValidityDate, false);
- }
- /** Add a DragSensitive entry valid after a limit date.<br>
- * Using <code>addDragSensitiveValidAfter(entry, t)</code> will make <code>entry</code>
- * valid in [t, +∞[ (note the closed bracket).
- * @param dragSensitive DragSensitive entry
- * @param earliestValidityDate date after which the entry is valid
- * (must be different from <b>all</b> dates already used for transitions)
- */
- public void addDragSensitiveValidAfter(final DragSensitive dragSensitive, final AbsoluteDate earliestValidityDate) {
- dragSensitiveTimeSpanMap.addValidAfter(changeDragParameterDriversNames(dragSensitive,
- earliestValidityDate,
- DATE_AFTER),
- earliestValidityDate, false);
- }
- /** Get the {@link DragSensitive} model valid at a date.
- * @param date the date of validity
- * @return the DragSensitive model valid at date
- */
- public DragSensitive getDragSensitive(final AbsoluteDate date) {
- return dragSensitiveTimeSpanMap.get(date);
- }
- /** Get the {@link DragSensitive} {@link Span} containing a specified date.
- * @param date date belonging to the desired time span
- * @return the DragSensitive time span containing the specified date
- */
- public Span<DragSensitive> getDragSensitiveSpan(final AbsoluteDate date) {
- return dragSensitiveTimeSpanMap.getSpan(date);
- }
- /** Extract a range of the {@link DragSensitive} map.
- * <p>
- * The object returned will be a new independent instance that will contain
- * only the transitions that lie in the specified range.
- * </p>
- * See the {@link TimeSpanMap#extractRange TimeSpanMap.extractRange method} for more.
- * @param start earliest date at which a transition is included in the range
- * (may be set to {@link AbsoluteDate#PAST_INFINITY} to keep all early transitions)
- * @param end latest date at which a transition is included in the r
- * (may be set to {@link AbsoluteDate#FUTURE_INFINITY} to keep all late transitions)
- * @return a new TimeSpanMap instance of DragSensitive with all transitions restricted to the specified range
- */
- public TimeSpanMap<DragSensitive> extractDragSensitiveRange(final AbsoluteDate start, final AbsoluteDate end) {
- return dragSensitiveTimeSpanMap.extractRange(start, end);
- }
- /** Get the {@link Transition}s of the drag sensitive time span map.
- * @return the {@link Transition}s for the drag sensitive time span map
- * @deprecated as of 11.1, replaced by {@link #getFirstSpan()}
- */
- @Deprecated
- public NavigableSet<Transition<DragSensitive>> getTransitions() {
- return dragSensitiveTimeSpanMap.getTransitions();
- }
- /** Get the first {@link Span time span} of the drag sensitive time span map.
- * @return the first {@link Span time span} of the drag sensitive time span map
- * @since 11.1
- */
- public Span<DragSensitive> getFirstSpan() {
- return dragSensitiveTimeSpanMap.getFirstSpan();
- }
- /** {@inheritDoc} */
- @Override
- public Vector3D acceleration(final SpacecraftState s, final double[] parameters) {
- // Local atmospheric density
- final AbsoluteDate date = s.getDate();
- final Frame frame = s.getFrame();
- final Vector3D position = s.getPVCoordinates().getPosition();
- final double rho = atmosphere.getDensity(date, position, frame);
- // Spacecraft relative velocity with respect to the atmosphere
- final Vector3D vAtm = atmosphere.getVelocity(date, position, frame);
- final Vector3D relativeVelocity = vAtm.subtract(s.getPVCoordinates().getVelocity());
- // Extract the proper parameters valid at date from the input array
- final double[] extractedParameters = extractParameters(parameters, date);
- // Compute and return drag acceleration
- return getDragSensitive(date).dragAcceleration(date, frame, position, s.getAttitude().getRotation(),
- s.getMass(), rho, relativeVelocity, extractedParameters);
- }
- /** {@inheritDoc} */
- @SuppressWarnings("unchecked")
- @Override
- public <T extends CalculusFieldElement<T>> FieldVector3D<T> acceleration(final FieldSpacecraftState<T> s,
- final T[] parameters) {
- // Local atmospheric density
- final FieldAbsoluteDate<T> date = s.getDate();
- final Frame frame = s.getFrame();
- final FieldVector3D<T> position = s.getPVCoordinates().getPosition();
- // Density and its derivatives
- final T rho;
- // Check for faster computation dedicated to derivatives with respect to state
- // Using finite differences instead of automatic differentiation as it seems to be much
- // faster for the drag's derivatives' computation
- if (isGradientStateDerivative(s)) {
- rho = (T) this.getGradientDensityWrtStateUsingFiniteDifferences(date.toAbsoluteDate(), frame, (FieldVector3D<Gradient>) position);
- } else if (isDSStateDerivative(s)) {
- rho = (T) this.getDSDensityWrtStateUsingFiniteDifferences(date.toAbsoluteDate(), frame, (FieldVector3D<DerivativeStructure>) position);
- } else {
- rho = atmosphere.getDensity(date, position, frame);
- }
- // Spacecraft relative velocity with respect to the atmosphere
- final FieldVector3D<T> vAtm = atmosphere.getVelocity(date, position, frame);
- final FieldVector3D<T> relativeVelocity = vAtm.subtract(s.getPVCoordinates().getVelocity());
- // Extract the proper parameters valid at date from the input array
- final T[] extractedParameters = extractParameters(parameters, date);
- // Compute and return drag acceleration
- return getDragSensitive(date.toAbsoluteDate()).dragAcceleration(date, frame, position, s.getAttitude().getRotation(),
- s.getMass(), rho, relativeVelocity, extractedParameters);
- }
- /**{@inheritDoc}
- * <p>
- * A date detector is used to cleanly stop the propagator and reset
- * the state derivatives at transition dates.
- * </p>
- */
- @Override
- public Stream<EventDetector> getEventsDetectors() {
- // Get the transitions' dates from the TimeSpanMap
- final AbsoluteDate[] transitionDates = getTransitionDates();
- // Initialize the date detector
- final DateDetector datesDetector = new DateDetector(transitionDates[0]).
- withMaxCheck(60.).
- withHandler((SpacecraftState state, DateDetector d, boolean increasing) -> {
- return Action.RESET_DERIVATIVES;
- });
- // Add all transitions' dates to the date detector
- for (int i = 1; i < transitionDates.length; i++) {
- datesDetector.addEventDate(transitionDates[i]);
- }
- // Return the detector
- return Stream.of(datesDetector);
- }
- /** {@inheritDoc}
- * <p>
- * A date detector is used to cleanly stop the propagator and reset
- * the state derivatives at transition dates.
- * </p>
- */
- @Override
- public <T extends CalculusFieldElement<T>> Stream<FieldEventDetector<T>> getFieldEventsDetectors(final Field<T> field) {
- // Get the transitions' dates from the TimeSpanMap
- final AbsoluteDate[] transitionDates = getTransitionDates();
- // Initialize the date detector
- final FieldDateDetector<T> datesDetector =
- new FieldDateDetector<>(new FieldAbsoluteDate<>(field, transitionDates[0])).
- withMaxCheck(field.getZero().add(60.)).
- withHandler((FieldSpacecraftState<T> state, FieldDateDetector<T> d, boolean increasing) -> {
- return Action.RESET_DERIVATIVES;
- });
- // Add all transitions' dates to the date detector
- for (int i = 1; i < transitionDates.length; i++) {
- datesDetector.addEventDate(new FieldAbsoluteDate<>(field, transitionDates[i]));
- }
- // Return the detector
- return Stream.of(datesDetector);
- }
- /** {@inheritDoc}
- * <p>
- * All the parameter drivers of all DragSensitive models are returned in an array.
- * Models are ordered chronologically.
- * </p>
- */
- @Override
- public List<ParameterDriver> getParametersDrivers() {
- // Get all transitions from the TimeSpanMap
- final List<ParameterDriver> listParameterDrivers = new ArrayList<>();
- // Loop on the spans
- for (Span<DragSensitive> span = getFirstSpan(); span != null; span = span.next()) {
- // Add all the parameter drivers of the span
- for (ParameterDriver driver : span.getData().getDragParametersDrivers()) {
- // Add the driver only if the name does not exist already
- if (!findByName(listParameterDrivers, driver.getName())) {
- listParameterDrivers.add(driver);
- }
- }
- }
- // Return an array of parameter drivers with no duplicated name
- return listParameterDrivers;
- }
- /** Extract the proper parameter drivers' values from the array in input of the
- * {@link #acceleration(SpacecraftState, double[]) acceleration} method.
- * Parameters are filtered given an input date.
- * @param parameters the input parameters array
- * @param date the date
- * @return the parameters given the date
- */
- public double[] extractParameters(final double[] parameters, final AbsoluteDate date) {
- // Get the drag parameter drivers of the date
- final List<ParameterDriver> dragParameterDriver = getDragSensitive(date).getDragParametersDrivers();
- // Find out the indexes of the parameters in the whole array of parameters
- final List<ParameterDriver> allParameters = getParametersDrivers();
- final double[] outParameters = new double[dragParameterDriver.size()];
- int index = 0;
- for (int i = 0; i < allParameters.size(); i++) {
- final String driverName = allParameters.get(i).getName();
- for (ParameterDriver dragDriver : dragParameterDriver) {
- if (dragDriver.getName().equals(driverName)) {
- outParameters[index++] = parameters[i];
- }
- }
- }
- return outParameters;
- }
- /** Extract the proper parameter drivers' values from the array in input of the
- * {@link #acceleration(FieldSpacecraftState, CalculusFieldElement[]) acceleration} method.
- * Parameters are filtered given an input date.
- * @param parameters the input parameters array
- * @param date the date
- * @param <T> extends CalculusFieldElement
- * @return the parameters given the date
- */
- public <T extends CalculusFieldElement<T>> T[] extractParameters(final T[] parameters,
- final FieldAbsoluteDate<T> date) {
- // Get the drag parameter drivers of the date
- final List<ParameterDriver> dragPD = getDragSensitive(date.toAbsoluteDate()).getDragParametersDrivers();
- // Find out the indexes of the parameters in the whole array of parameters
- final List<ParameterDriver> allParameters = getParametersDrivers();
- final T[] outParameters = MathArrays.buildArray(date.getField(), dragPD.size());
- int index = 0;
- for (int i = 0; i < allParameters.size(); i++) {
- final String driverName = allParameters.get(i).getName();
- for (ParameterDriver dragDriver : dragPD) {
- if (dragDriver.getName().equals(driverName)) {
- outParameters[index++] = parameters[i];
- }
- }
- }
- return outParameters;
- }
- /** Find if a parameter driver with a given name already exists in a list of parameter drivers.
- * @param driversList the list of parameter drivers
- * @param name the parameter driver's name to filter with
- * @return true if the name was found, false otherwise
- */
- private boolean findByName(final List<ParameterDriver> driversList, final String name) {
- for (final ParameterDriver d : driversList) {
- if (d.getName().equals(name)) {
- return true;
- }
- }
- return false;
- }
- /** Get the dates of the transitions for the drag sensitive models {@link TimeSpanMap}.
- * @return dates of the transitions for the drag sensitive models {@link TimeSpanMap}
- */
- private AbsoluteDate[] getTransitionDates() {
- // Get all transitions
- final List<AbsoluteDate> listDates = new ArrayList<>();
- // Extract all the transitions' dates
- for (Transition<DragSensitive> transition = getFirstSpan().getEndTransition(); transition != null; transition = transition.next()) {
- listDates.add(transition.getDate());
- }
- // Return the array of transition dates
- return listDates.toArray(new AbsoluteDate[0]);
- }
- /** Change the parameter drivers names of a {@link DragSensitive} model, if needed.
- * <p>
- * This is done to avoid that several parameter drivers have the same name.<br>
- * It is done only if the user hasn't modify the DragSensitive parameter drivers default names.
- * </p>
- * @param dragSensitive the DragSensitive model
- * @param date the date used in the parameter driver's name
- * @param datePrefix the date prefix used in the parameter driver's name
- * @return the DragSensitive with its drivers' names changed
- */
- private DragSensitive changeDragParameterDriversNames(final DragSensitive dragSensitive,
- final AbsoluteDate date,
- final String datePrefix) {
- // Loop on the parameter drivers of the DragSensitive model
- for (ParameterDriver driver: dragSensitive.getDragParametersDrivers()) {
- final String driverName = driver.getName();
- // If the name is the default name for DragSensitive parameter drivers
- // Modify the name to add the prefix and the date
- if (driverName.equals(DragSensitive.DRAG_COEFFICIENT) || driverName.equals(DragSensitive.LIFT_RATIO)) {
- driver.setName(driverName + datePrefix + date.toString(timeScale));
- }
- }
- return dragSensitive;
- }
- }