Propagator.java

  1. /* Copyright 2002-2021 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.propagation;

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

  22. import org.hipparchus.geometry.euclidean.threed.Rotation;
  23. import org.orekit.attitudes.AttitudeProvider;
  24. import org.orekit.attitudes.InertialProvider;
  25. import org.orekit.frames.Frame;
  26. import org.orekit.frames.Frames;
  27. import org.orekit.propagation.events.EventDetector;
  28. import org.orekit.propagation.sampling.OrekitFixedStepHandler;
  29. import org.orekit.propagation.sampling.OrekitStepHandler;
  30. import org.orekit.propagation.sampling.StepHandlerMultiplexer;
  31. import org.orekit.time.AbsoluteDate;
  32. import org.orekit.utils.PVCoordinatesProvider;

  34. /** This interface provides a way to propagate an orbit at any time.
  35.  *
  36.  * <p>This interface is the top-level abstraction for orbit propagation.
  37.  * It only allows propagation to a predefined date.
  38.  * It is implemented by analytical models which have no time limit,
  39.  * by orbit readers based on external data files, by numerical integrators
  40.  * using rich force models and by continuous models built after numerical
  41.  * integration has been completed and dense output data as been
  42.  * gathered.</p>
  43.  * <p>Note that one single propagator cannot be called from multiple threads.
  44.  * Its configuration can be changed as there is at least a {@link
  45.  * #resetInitialState(SpacecraftState)} method, and even propagators that do
  46.  * not support resetting state (like the {@link
  47.  * org.orekit.propagation.analytical.tle.TLEPropagator TLEPropagator} do
  48.  * cache some internal data during computation. However, as long as they
  49.  * are configured with independent building blocks (mainly event handlers
  50.  * and step handlers that may preserve some internal state), and as long
  51.  * as they are called from one thread only, they <em>can</em> be used in
  52.  * multi-threaded applications. Synchronizing several propagators to run in
  53.  * parallel is also possible using {@link PropagatorsParallelizer}.</p>
  54.  * @author Luc Maisonobe
  55.  * @author V&eacute;ronique Pommier-Maurussane
  56.  *
  57.  */

  59. public interface Propagator extends PVCoordinatesProvider {

  61.     /** Default mass. */
  62.     double DEFAULT_MASS = 1000.0;

  64.     /**
  65.      * Get a default law using the given frames.
  66.      *
  67.      * @param frames the set of frames to use.
  68.      * @return attitude law.
  69.      */
  70.     static AttitudeProvider getDefaultLaw(final Frames frames) {
  71.         return new InertialProvider(Rotation.IDENTITY, frames.getEME2000());
  72.     }

  74.     /** Get the multiplexer holding all step handlers.
  75.      * @return multiplexer holding all step handlers
  76.      * @since 11.0
  77.      */
  78.     StepHandlerMultiplexer getMultiplexer();

  80.     /** Remove all step handlers.
  81.      * <p>This convenience method is equivalent to call {@code getMultiplexer().clear()}</p>
  82.      * @see #getMultiplexer()
  83.      * @see StepHandlerMultiplexer#clear()
  84.      * @since 11.0
  85.      */
  86.     default void clearStepHandlers() {
  87.         getMultiplexer().clear();
  88.     }

  90.     /** Set a single handler for fixed stepsizes.
  91.      * <p>This convenience method is equivalent to call {@code getMultiplexer().clear()}
  92.      * followed by {@code getMultiplexer().add(h, handler)}</p>
  93.      * @param h fixed stepsize (s)
  94.      * @param handler handler called at the end of each finalized step
  95.      * @see #getMultiplexer()
  96.      * @see StepHandlerMultiplexer#add(double, OrekitFixedStepHandler)
  97.      * @since 11.0
  98.      */
  99.     default void setStepHandler(final double h, final OrekitFixedStepHandler handler) {
  100.         getMultiplexer().clear();
  101.         getMultiplexer().add(h, handler);
  102.     }

  104.     /** Set a single handler for variable stepsizes.
  105.      * <p>This convenience method is equivalent to call {@code getMultiplexer().clear()}
  106.      * followed by {@code getMultiplexer().add(handler)}</p>
  107.      * @param handler handler called at the end of each finalized step
  108.      * @see #getMultiplexer()
  109.      * @see StepHandlerMultiplexer#add(OrekitStepHandler)
  110.      * @since 11.0
  111.      */
  112.     default void setStepHandler(final OrekitStepHandler handler) {
  113.         getMultiplexer().clear();
  114.         getMultiplexer().add(handler);
  115.     }

  117.     /**
  118.      * Set up an ephemeris generator that will monitor the propagation for building
  119.      * an ephemeris from it once completed.
  120.      *
  121.      * <p>
  122.      * This generator can be used when the user needs fast random access to the orbit
  123.      * state at any time between the initial and target times. A typical example is the
  124.      * implementation of search and iterative algorithms that may navigate forward and
  125.      * backward inside the propagation range before finding their result even if the
  126.      * propagator used is integration-based and only goes from one initial time to one
  127.      * target time.
  128.      * </p>
  129.      * <p>
  130.      * Beware that when used with integration-based propagators, the generator will
  131.      * store <strong>all</strong> intermediate results. It is therefore memory intensive
  132.      * for long integration-based ranges and high precision/short time steps. When
  133.      * used with analytical propagators, the generator only stores start/stop time
  134.      * and a reference to the analytical propagator itself to call it back as needed,
  135.      * so it is less memory intensive.
  136.      * </p>
  137.      * <p>
  138.      * The returned ephemeris generator will be initially empty, it will be filled
  139.      * with propagation data when a subsequent call to either {@link #propagate(AbsoluteDate)
  140.      * propagate(target)} or {@link #propagate(AbsoluteDate, AbsoluteDate)
  141.      * propagate(start, target)} is called. The proper way to use this method is
  142.      * therefore to do:
  143.      * </p>
  144.      * <pre>
  145.      *   EphemerisGenerator generator = propagator.getEphemerisGenerator();
  146.      *   propagator.propagate(target);
  147.      *   BoundedPropagator ephemeris = generator.getGeneratedEphemeris();
  148.      * </pre>
  149.      * @return ephemeris generator
  150.      */
  151.     EphemerisGenerator getEphemerisGenerator();

  153.     /** Get the propagator initial state.
  154.      * @return initial state
  155.      */
  156.     SpacecraftState getInitialState();

  158.     /** Reset the propagator initial state.
  159.      * @param state new initial state to consider
  160.      */
  161.     void resetInitialState(SpacecraftState state);

  163.     /** Add a set of user-specified state parameters to be computed along with the orbit propagation.
  164.      * @param additionalStateProvider provider for additional state
  165.      */
  166.     void addAdditionalStateProvider(AdditionalStateProvider additionalStateProvider);

  168.     /** Get an unmodifiable list of providers for additional state.
  169.      * @return providers for the additional states
  170.      */
  171.     List<AdditionalStateProvider> getAdditionalStateProviders();

  173.     /** Check if an additional state is managed.
  174.      * <p>
  175.      * Managed states are states for which the propagators know how to compute
  176.      * its evolution. They correspond to additional states for which an
  177.      * {@link AdditionalStateProvider additional state provider} has been registered
  178.      * by calling the {@link #addAdditionalStateProvider(AdditionalStateProvider)
  179.      * addAdditionalStateProvider} method. If the propagator is an {@link
  180.      * org.orekit.propagation.integration.AbstractIntegratedPropagator integrator-based
  181.      * propagator}, the states for which a set of {@link
  182.      * org.orekit.propagation.integration.AdditionalEquations additional equations} has
  183.      * been registered by calling the {@link
  184.      * org.orekit.propagation.integration.AbstractIntegratedPropagator#addAdditionalEquations(
  185.      * org.orekit.propagation.integration.AdditionalEquations) addAdditionalEquations}
  186.      * method are also counted as managed additional states.
  187.      * </p>
  188.      * <p>
  189.      * Additional states that are present in the {@link #getInitialState() initial state}
  190.      * but have no evolution method registered are <em>not</em> considered as managed states.
  191.      * These unmanaged additional states are not lost during propagation, though. Their
  192.      * value are piecewise constant between state resets that may change them if some
  193.      * event handler {@link
  194.      * org.orekit.propagation.events.handlers.EventHandler#resetState(EventDetector,
  195.      * SpacecraftState) resetState} method is called at an event occurrence and happens
  196.      * to change the unmanaged additional state.
  197.      * </p>
  198.      * @param name name of the additional state
  199.      * @return true if the additional state is managed
  200.      */
  201.     boolean isAdditionalStateManaged(String name);

  203.     /** Get all the names of all managed states.
  204.      * @return names of all managed states
  205.      */
  206.     String[] getManagedAdditionalStates();

  208.     /** Add an event detector.
  209.      * @param detector event detector to add
  210.      * @see #clearEventsDetectors()
  211.      * @see #getEventsDetectors()
  212.      * @param <T> class type for the generic version
  213.      */
  214.     <T extends EventDetector> void addEventDetector(T detector);

  216.     /** Get all the events detectors that have been added.
  217.      * @return an unmodifiable collection of the added detectors
  218.      * @see #addEventDetector(EventDetector)
  219.      * @see #clearEventsDetectors()
  220.      */
  221.     Collection<EventDetector> getEventsDetectors();

  223.     /** Remove all events detectors.
  224.      * @see #addEventDetector(EventDetector)
  225.      * @see #getEventsDetectors()
  226.      */
  227.     void clearEventsDetectors();

  229.     /** Get attitude provider.
  230.      * @return attitude provider
  231.      */
  232.     AttitudeProvider getAttitudeProvider();

  234.     /** Set attitude provider.
  235.      * @param attitudeProvider attitude provider
  236.      */
  237.     void setAttitudeProvider(AttitudeProvider attitudeProvider);

  239.     /** Get the frame in which the orbit is propagated.
  240.      * <p>
  241.      * The propagation frame is the definition frame of the initial
  242.      * state, so this method should be called after this state has
  243.      * been set, otherwise it may return null.
  244.      * </p>
  245.      * @return frame in which the orbit is propagated
  246.      * @see #resetInitialState(SpacecraftState)
  247.      */
  248.     Frame getFrame();

  250.     /** Propagate towards a target date.
  251.      * <p>Simple propagators use only the target date as the specification for
  252.      * computing the propagated state. More feature rich propagators can consider
  253.      * other information and provide different operating modes or G-stop
  254.      * facilities to stop at pinpointed events occurrences. In these cases, the
  255.      * target date is only a hint, not a mandatory objective.</p>
  256.      * @param target target date towards which orbit state should be propagated
  257.      * @return propagated state
  258.      */
  259.     SpacecraftState propagate(AbsoluteDate target);

  261.     /** Propagate from a start date towards a target date.
  262.      * <p>Those propagators use a start date and a target date to
  263.      * compute the propagated state. For propagators using event detection mechanism,
  264.      * if the provided start date is different from the initial state date, a first,
  265.      * simple propagation is performed, without processing any event computation.
  266.      * Then complete propagation is performed from start date to target date.</p>
  267.      * @param start start date from which orbit state should be propagated
  268.      * @param target target date to which orbit state should be propagated
  269.      * @return propagated state
  270.      */
  271.     SpacecraftState propagate(AbsoluteDate start, AbsoluteDate target);

  273. }
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