Package org.orekit.propagation.events

Class BooleanDetector

java.lang.Object
org.orekit.propagation.events.AbstractDetector<BooleanDetector>
org.orekit.propagation.events.BooleanDetector
All Implemented Interfaces:
EventDetector
public class BooleanDetector extends AbstractDetector<BooleanDetector>
This class provides AND and OR operations for event detectors. This class treats positive values of the g function as true and negative values as false.

One example for an imaging satellite might be to only detect events when a satellite is overhead (elevation > 0) AND when the ground point is sunlit (Sun elevation > 0). Another slightly contrived example using the OR operator would be to detect access to a set of ground stations and only report events when the satellite enters or leaves the field of view of the set, but not hand-offs between the ground stations.

For the BooleanDetector is important that the sign of the g function of the underlying event detector is not arbitrary, but has a semantic meaning, e.g. in or out, true or false. This class works well with event detectors that detect entry to or exit from a region, e.g. EclipseDetector, ElevationDetector, LatitudeCrossingDetector. Using this detector with detectors that are not based on entry to or exit from a region, e.g. DateDetector, LongitudeCrossingDetector, will likely lead to unexpected results. To apply conditions to this latter type of event detectors a EventEnablingPredicateFilter is usually more appropriate.

Author:
Evan Ward
See Also:

  • Constructor Details

    • BooleanDetector

      protected BooleanDetector(List<EventDetector> detectors, BooleanEventFunction eventFunction, EventDetectionSettings detectionSettings, EventHandler newHandler)
      Protected constructor with all the parameters.
      Parameters:
      detectors - the operands.
      eventFunction - reduced event function according to boolean operator.
      detectionSettings - event detection settings.
      newHandler - event handler.
      Since:
      14.0

  • Method Details

    • andCombine

      public static BooleanDetector andCombine(EventDetector... detectors)
      Create a new event detector that is the logical AND of the given event detectors.

      The created event detector's g function is positive if and only if the g functions of all detectors in detectors are positive.

      The starting interval, threshold, and iteration count are set to the most stringent (minimum) of all the detectors. The event handlers of the underlying detectors are not used, instead the default handler is ContinueOnEvent.

      Parameters:
      detectors - the operands. Must contain at least one detector.
      Returns:
      a new event detector that is the logical AND of the operands.
      Throws:
      NoSuchElementException - if detectors is empty.
      See Also:

    • andCombine

      public static BooleanDetector andCombine(Collection<? extends EventDetector> detectors)
      Create a new event detector that is the logical AND of the given event detectors.

      The created event detector's g function is positive if and only if the g functions of all detectors in detectors are positive.

      The starting interval, threshold, and iteration count are set to the most stringent (minimum) of the detectors. The event handlers of the underlying detectors are not used, instead the default handler is ContinueOnEvent.

      Parameters:
      detectors - the operands. Must contain at least one detector.
      Returns:
      a new event detector that is the logical AND of the operands.
      Throws:
      NoSuchElementException - if detectors is empty.
      See Also:

    • orCombine

      public static BooleanDetector orCombine(EventDetector... detectors)
      Create a new event detector that is the logical OR of the given event detectors.

      The created event detector's g function is positive if and only if at least one of g functions of the event detectors in detectors is positive.

      The starting interval, threshold, and iteration count are set to the most stringent (minimum) of the detectors. The event handlers of the underlying EventDetectors are not used, instead the default handler is ContinueOnEvent.

      Parameters:
      detectors - the operands. Must contain at least one detector.
      Returns:
      a new event detector that is the logical OR of the operands.
      Throws:
      NoSuchElementException - if detectors is empty.
      See Also:

    • orCombine

      public static BooleanDetector orCombine(Collection<? extends EventDetector> detectors)
      Create a new event detector that is the logical OR of the given event detectors.

      The created event detector's g function is positive if and only if at least one of g functions of the event detectors in detectors is positive.

      The starting interval, threshold, and iteration count are set to the most stringent (minimum) of the detectors. The event handlers of the underlying EventDetectors are not used, instead the default handler is ContinueOnEvent.

      Parameters:
      detectors - the operands. Must contain at least one detector.
      Returns:
      a new event detector that is the logical OR of the operands.
      Throws:
      NoSuchElementException - if detectors is empty.
      See Also:

    • notCombine

      public static NegateDetector notCombine(EventDetector detector)
      Create a new event detector that negates the g function of another detector.

      This detector will be initialized with the same EventDetector.getMaxCheckInterval(), EventDetector.getThreshold(), and EventDetector.getMaxIterationCount() as detector. The event handler of the underlying detector is not used, instead the default handler is ContinueOnEvent.

      Parameters:
      detector - to negate.
      Returns:
      a new event detector whose g function is the same magnitude but opposite sign of detector.
      See Also:

    • g

      public double g(SpacecraftState s)
      Description copied from interface: EventDetector
      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

    • create

      protected BooleanDetector create(EventDetectionSettings detectionSettings, EventHandler newHandler)
      Description copied from class: AbstractDetector
      Build a new instance.
      Specified by:
      create in class AbstractDetector<BooleanDetector>
      Parameters:
      detectionSettings - detection settings
      newHandler - event handler to call at event occurrences
      Returns:
      a new instance of the appropriate sub-type

    • init

      public void init(SpacecraftState s0, AbsoluteDate t)
      Description copied from class: AbstractDetector
      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.

      This implementation sets the direction of propagation and initializes the event handler. If a subclass overrides this method it should call super.init(s0, t).

      Specified by:
      init in interface EventDetector
      Overrides:
      init in class AbstractDetector<BooleanDetector>
      Parameters:
      s0 - initial state
      t - target time for the integration

    • reset

      public void reset(SpacecraftState state, AbsoluteDate target)
      Description copied from interface: EventDetector
      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

    • finish

      public void finish(SpacecraftState state)
      Description copied from interface: EventDetector
      This method finalizes the event detector's job.
      Parameters:
      state - state at propagation end

    • getDetectors

      public List<EventDetector> getDetectors()
      Get the list of original detectors.
      Returns:
      the list of original detectors
      Since:
      10.2