Package org.orekit.propagation.events

Interface EventDetector

All Known Subinterfaces:
DetectorModifier
All Known Implementing Classes:
AbstractDetector, AbstractGeographicalDetector, AbstractTopocentricDetector, AlignmentDetector, AltitudeDetector, AngularSeparationDetector, AngularSeparationFromSatelliteDetector, ApsideDetector, AttitudesSequence.Switch, AttitudesSwitcher.InstantaneousSwitch, BetaAngleDetector, BooleanDetector, CylindricalShadowEclipseDetector, DateDetector, EclipseDetector, ElevationDetector, ElevationExtremumDetector, EventEnablingPredicateFilter, EventShifter, EventSlopeFilter, ExtremumAngularSeparationDetector, ExtremumApproachDetector, FieldOfViewDetector, FootprintOverlapDetector, FunctionalDetector, GeographicZoneDetector, GroundAtNightDetector, GroundFieldOfViewDetector, ImpulseManeuver, InterSatDirectViewDetector, LatitudeCrossingDetector, LatitudeExtremumDetector, LatitudeRangeCrossingDetector, LongitudeCrossingDetector, LongitudeExtremumDetector, LongitudeRangeCrossingDetector, MagneticFieldDetector, ManeuverTriggerDetector, NegateDetector, NodeDetector, ParameterDrivenDateIntervalDetector, PlaneCrossingDetector, PositionAngleDetector, RelativeDistanceDetector, SingleDateDetector, TimeIntervalDetector
public interface EventDetector
This interface represents space-dynamics aware events detectors.

It mirrors the ODEEventHandler interface from Hipparchus but provides a space-dynamics interface to the methods.

Events detectors are a useful solution to meet the requirements of propagators concerning discrete conditions. The state of each event detector is queried by the propagator from time to time, at least once every max check interval but it may be more frequent. When the sign of the underlying g switching function changes, a root-finding algorithm is run to precisely locate the event, down to a configured convergence threshold. The max check interval is therefore devoted to separate roots and is often much larger than the convergence threshold.

The physical meaning of the g switching function is not really used by the event detection algorithms. Its varies from event detector to event detector. One example would be a visibility detector that could use the angular elevation of the satellite above horizon as a g switching function. In this case, the function would switch from negative to positive when the satellite raises above horizon and it would switch from positive to negative when it sets backs below horizon. Another example would be an apside detector that could use the dot product of position and velocity. In this case, the function would switch from negative to positive when the satellite crosses periapsis and it would switch from positive to negative when the satellite crosses apoapsis.

When the precise state at which the g switching function changes has been located, the corresponding event is triggered, by calling the eventOccurred method from the associated handler. The method can do whatever it needs with the event (logging it, performing some processing, ignore it ...). The return value of the method will be used by the propagator to stop or resume propagation, possibly changing the state vector.

Author:
Luc Maisonobe, Véronique Pommier-Maurussane

  • Method Details

    • of

      static EventDetector of(EventFunction eventFunction)
      Builds instance from event function only. Uses default handler and detection settings.
      Parameters:
      eventFunction - event function
      Returns:
      event detector
      Since:
      14.0

    • of

      static EventDetector of(EventFunction eventFunction, EventHandler eventHandler)
      Builds instance from event function and handler. Uses default detection settings.
      Parameters:
      eventFunction - event function
      eventHandler - handler
      Returns:
      event detector
      Since:
      14.0

    • of

      static EventDetector of(EventFunction eventFunction, EventHandler eventHandler, EventDetectionSettings eventDetectionSettings)
      Builds instance from event function, handler and detection settings.
      Parameters:
      eventFunction - event function
      eventHandler - handler
      eventDetectionSettings - detection settings
      Returns:
      event detector
      Since:
      14.0

    • init

      default void init(SpacecraftState s0, AbsoluteDate t)
      Initialize event detector at the start of a propagation.

      This method is called once at the start of the propagation. It may be used by the event handler to initialize some internal data if needed.

      The default implementation initializes the handler.

      Parameters:
      s0 - initial state
      t - target time for the integration

    • reset

      default void reset(SpacecraftState state, AbsoluteDate target)
      Reset the event detector during propagation when the state is modified by an event or an additional data provider.

      The default implementation does nothing.

      Parameters:
      state - current state
      target - target time for the integration
      Since:
      13.0

    • g

      double g(SpacecraftState s)
      Compute the value of the switching function. This function must be continuous (at least in its roots neighborhood), as the integrator will need to find its roots to locate the events.
      Parameters:
      s - the current state information: date, kinematics, attitude
      Returns:
      value of the switching function

    • getEventFunction

      default EventFunction getEventFunction()
      Get the event function. It defines g both for double and Field.
      Returns:
      event function
      Since:
      14.0

    • getThreshold

      default double getThreshold()
      Get the convergence threshold in the event time search.
      Returns:
      convergence threshold (s)

    • getMaxCheckInterval

      default AdaptableInterval getMaxCheckInterval()
      Get maximal time interval between switching function checks.
      Returns:
      maximal time interval (s) between switching function checks

    • getMaxIterationCount

      default int getMaxIterationCount()
      Get maximal number of iterations in the event time search.
      Returns:
      maximal number of iterations in the event time search

    • getHandler

      EventHandler getHandler()
      Get the handler.
      Returns:
      event handler to call at event occurrences
      Since:
      12.0

    • finish

      default void finish(SpacecraftState state)
      This method finalizes the event detector's job.
      Parameters:
      state - state at propagation end
      Since:
      12.2

    • getDetectionSettings

      default EventDetectionSettings getDetectionSettings()
      Getter for the settings.
      Returns:
      detection settings
      Since:
      12.2