ForceModel.java

  1. /* Copyright 2002-2022 CS GROUP
  2.  * Licensed to CS GROUP (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.forces;

  19. import java.util.List;
  20. import java.util.stream.Stream;

  22. import org.hipparchus.CalculusFieldElement;
  23. import org.hipparchus.Field;
  24. import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
  25. import org.hipparchus.geometry.euclidean.threed.Vector3D;
  26. import org.hipparchus.util.MathArrays;
  27. import org.orekit.propagation.FieldSpacecraftState;
  28. import org.orekit.propagation.SpacecraftState;
  29. import org.orekit.propagation.events.EventDetector;
  30. import org.orekit.propagation.events.FieldEventDetector;
  31. import org.orekit.propagation.numerical.FieldTimeDerivativesEquations;
  32. import org.orekit.propagation.numerical.TimeDerivativesEquations;
  33. import org.orekit.time.AbsoluteDate;
  34. import org.orekit.time.FieldAbsoluteDate;
  35. import org.orekit.utils.ParameterDriver;

  37. /** This interface represents a force modifying spacecraft motion.
  38.  *
  39.  * <p>
  40.  * Objects implementing this interface are intended to be added to a
  41.  * {@link org.orekit.propagation.numerical.NumericalPropagator numerical propagator}
  42.  * before the propagation is started.
  43.  *
  44.  * <p>
  45.  * The propagator will call at each step the {@link #addContribution(SpacecraftState,
  46.  * TimeDerivativesEquations)} method. The force model instance will extract all the
  47.  * state data it needs (date, position, velocity, frame, attitude, mass) from the first
  48.  * parameter. From these state data, it will compute the perturbing acceleration. It
  49.  * will then add this acceleration to the second parameter which will take thins
  50.  * contribution into account and will use the Gauss equations to evaluate its impact
  51.  * on the global state derivative.
  52.  * </p>
  53.  * <p>
  54.  * Force models which create discontinuous acceleration patterns (typically for maneuvers
  55.  * start/stop or solar eclipses entry/exit) must provide one or more {@link
  56.  * org.orekit.propagation.events.EventDetector events detectors} to the
  57.  * propagator thanks to their {@link #getEventsDetectors()} method. This method
  58.  * is called once just before propagation starts. The events states will be checked by
  59.  * the propagator to ensure accurate propagation and proper events handling.
  60.  * </p>
  61.  *
  62.  * @author Mathieu Rom&eacute;ro
  63.  * @author Luc Maisonobe
  64.  * @author V&eacute;ronique Pommier-Maurussane
  65.  */
  66. public interface ForceModel {

  68.     /**
  69.      * Initialize the force model at the start of propagation. This method will be called
  70.      * before any calls to {@link #addContribution(SpacecraftState, TimeDerivativesEquations)},
  71.      * {@link #addContribution(FieldSpacecraftState, FieldTimeDerivativesEquations)},
  72.      * {@link #acceleration(SpacecraftState, double[])} or {@link #acceleration(FieldSpacecraftState, CalculusFieldElement[])}
  73.      *
  74.      * <p> The default implementation of this method does nothing.</p>
  75.      *
  76.      * @param initialState spacecraft state at the start of propagation.
  77.      * @param target       date of propagation. Not equal to {@code initialState.getDate()}.
  78.      */
  79.     default void init(SpacecraftState initialState, AbsoluteDate target) {
  80.     }

  82.     /**
  83.      * Initialize the force model at the start of propagation. This method will be called
  84.      * before any calls to {@link #addContribution(SpacecraftState, TimeDerivativesEquations)},
  85.      * {@link #addContribution(FieldSpacecraftState, FieldTimeDerivativesEquations)},
  86.      * {@link #acceleration(SpacecraftState, double[])} or {@link #acceleration(FieldSpacecraftState, CalculusFieldElement[])}
  87.      *
  88.      * <p> The default implementation of this method does nothing.</p>
  89.      *
  90.      * @param initialState spacecraft state at the start of propagation.
  91.      * @param target       date of propagation. Not equal to {@code initialState.getDate()}.
  92.      * @param <T> type of the elements
  93.      */
  94.     default <T extends CalculusFieldElement<T>> void init(FieldSpacecraftState<T> initialState, FieldAbsoluteDate<T> target) {
  95.         init(initialState.toSpacecraftState(), target.toAbsoluteDate());
  96.     }

  98.     /** Compute the contribution of the force model to the perturbing
  99.      * acceleration.
  100.      * <p>
  101.      * The default implementation simply adds the {@link #acceleration(SpacecraftState, double[]) acceleration}
  102.      * as a non-Keplerian acceleration.
  103.      * </p>
  104.      * @param s current state information: date, kinematics, attitude
  105.      * @param adder object where the contribution should be added
  106.      */
  107.     default void addContribution(SpacecraftState s, TimeDerivativesEquations adder) {
  108.         adder.addNonKeplerianAcceleration(acceleration(s, getParameters()));
  109.     }

  111.     /** Compute the contribution of the force model to the perturbing
  112.      * acceleration.
  113.      * @param s current state information: date, kinematics, attitude
  114.      * @param adder object where the contribution should be added
  115.      * @param <T> type of the elements
  116.      */
  117.     default <T extends CalculusFieldElement<T>> void addContribution(FieldSpacecraftState<T> s, FieldTimeDerivativesEquations<T> adder) {
  118.         adder.addNonKeplerianAcceleration(acceleration(s, getParameters(s.getDate().getField())));
  119.     }

  121.     /** Get force model parameters.
  122.      * @return force model parameters
  123.      * @since 9.0
  124.      */
  125.     default double[] getParameters() {
  126.         final List<ParameterDriver> drivers = getParametersDrivers();
  127.         final double[] parameters = new double[drivers.size()];
  128.         for (int i = 0; i < drivers.size(); ++i) {
  129.             parameters[i] = drivers.get(i).getValue();
  130.         }
  131.         return parameters;
  132.     }

  134.     /** Get force model parameters.
  135.      * @param field field to which the elements belong
  136.      * @param <T> type of the elements
  137.      * @return force model parameters
  138.      * @since 9.0
  139.      */
  140.     default <T extends CalculusFieldElement<T>> T[] getParameters(final Field<T> field) {
  141.         final List<ParameterDriver> drivers = getParametersDrivers();
  142.         final T[] parameters = MathArrays.buildArray(field, drivers.size());
  143.         for (int i = 0; i < drivers.size(); ++i) {
  144.             parameters[i] = field.getZero().add(drivers.get(i).getValue());
  145.         }
  146.         return parameters;
  147.     }

  149.     /** Check if force models depends on position only.
  150.      * @return true if force model depends on position only, false
  151.      * if it depends on velocity, either directly or due to a dependency
  152.      * on attitude
  153.      * @since 9.0
  154.      */
  155.     boolean dependsOnPositionOnly();

  157.     /** Compute acceleration.
  158.      * @param s current state information: date, kinematics, attitude
  159.      * @param parameters values of the force model parameters
  160.      * @return acceleration in same frame as state
  161.      * @since 9.0
  162.      */
  163.     Vector3D acceleration(SpacecraftState s, double[] parameters);

  165.     /** Compute acceleration.
  166.      * @param s current state information: date, kinematics, attitude
  167.      * @param parameters values of the force model parameters
  168.      * @return acceleration in same frame as state
  169.      * @param <T> type of the elements
  170.      * @since 9.0
  171.      */
  172.     <T extends CalculusFieldElement<T>> FieldVector3D<T> acceleration(FieldSpacecraftState<T> s, T[] parameters);

  174.     /** Get the discrete events related to the model.
  175.      * @return stream of events detectors
  176.      */
  177.     Stream<EventDetector> getEventsDetectors();

  179.     /** Get the discrete events related to the model.
  180.      * @param field field to which the state belongs
  181.      * @param <T> extends CalculusFieldElement&lt;T&gt;
  182.      * @return stream of events detectors
  183.      */
  184.     <T extends CalculusFieldElement<T>> Stream<FieldEventDetector<T>> getFieldEventsDetectors(Field<T> field);

  186.     /** Get the drivers for force model parameters.
  187.      * @return drivers for force model parameters
  188.      * @since 8.0
  189.      */
  190.     List<ParameterDriver> getParametersDrivers();

  192.     /** Get parameter value from its name.
  193.      * @param name parameter name
  194.      * @return parameter value
  195.      * @since 8.0
  196.      */
  197.     ParameterDriver getParameterDriver(String name);

  199.     /** Check if a parameter is supported.
  200.      * <p>Supported parameters are those listed by {@link #getParametersDrivers()}.</p>
  201.      * @param name parameter name to check
  202.      * @return true if the parameter is supported
  203.      * @see #getParametersDrivers()
  204.      */
  205.     boolean isSupported(String name);

  207. }
Created with JaCoCo 0.8.7.202105040129