Package org.orekit.propagation.events

Class EventEnablingPredicateFilter

  • All Implemented Interfaces:
    DetectorModifier, EventDetector
    public class EventEnablingPredicateFilter
extends Object
implements DetectorModifier
    Wrapper used to detect events only when enabled by an external predicated function.

    General events are defined implicitly by a g function crossing zero. This implies that during an orbit propagation, events are triggered at all zero crossings.

    Sometimes, users would like to enable or disable events by themselves, for example to trigger them only for certain orbits, or to check elevation maximums only when elevation itself is positive (i.e. they want to discard elevation maximums below ground). In these cases, looking precisely for all events location and triggering events that will later be ignored is a waste of computing time.

    Users can wrap a regular event detector in an instance of this class and provide this wrapping instance to a Propagator in order to avoid wasting time looking for uninteresting events. The wrapper will intercept the calls to the g function and to the eventOccurred method in order to ignore uninteresting events. The wrapped regular event detector will the see only the interesting events, i.e. either only events that occur when a user-provided event enabling predicate function is true, ignoring all events that occur when the event enabling predicate function is false. The number of calls to the g function will also be reduced.

    Since:
    7.1
    See Also:
    EventSlopeFilter

    • Constructor Detail

      • EventEnablingPredicateFilter

        public EventEnablingPredicateFilter​(EventDetector rawDetector,
                                    EnablingPredicate enabler)
        Wrap an event detector.
        Parameters:
        rawDetector - event detector to wrap (its detection settings are taken as well)
        enabler - event enabling predicate function to use

      • EventEnablingPredicateFilter

        public EventEnablingPredicateFilter​(EventDetectionSettings detectionSettings,
                                    EventDetector rawDetector,
                                    EnablingPredicate enabler)
        Constructor with full parameters.
        Parameters:
        detectionSettings - event detection settings
        rawDetector - event detector to wrap
        enabler - event enabling function to use
        Since:
        13.0

    • Method Detail

      • withDetectionSettings

        public EventEnablingPredicateFilter withDetectionSettings​(EventDetectionSettings settings)
        Builds a new instance from the input detection settings.
        Parameters:
        settings - event detection settings to be used
        Returns:
        a new detector

      • init

        public 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.

        Specified by:
        init in interface DetectorModifier
        Specified by:
        init in interface EventDetector
        Parameters:
        s0 - initial state
        t - target time for the integration

      • reset

        public 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.

        Specified by:
        reset in interface DetectorModifier
        Specified by:
        reset in interface EventDetector
        Parameters:
        state - current state
        target - target time for the integration

      • g

        public 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.
        Specified by:
        g in interface DetectorModifier
        Specified by:
        g in interface EventDetector
        Parameters:
        s - the current state information: date, kinematics, attitude
        Returns:
        value of the switching function

      • isForward

        public boolean isForward()
        Check if the current propagation is forward or backward.
        Returns:
        true if the current propagation is forward