Class NodeDetector

  • All Implemented Interfaces:
    EventDetector

    public class NodeDetector
    extends AbstractDetector<NodeDetector>
    Finder for node crossing events.

    This class finds equator crossing events (i.e. ascending or descending node crossing).

    The default implementation behavior is to continue propagation at descending node crossing and to stop propagation at ascending node crossing. This can be changed by calling AbstractDetector.withHandler(EventHandler) after construction.

    Beware that node detection will fail for almost equatorial orbits. If for example a node detector is used to trigger an ImpulseManeuver and the maneuver turn the orbit plane to equator, then the detector may completely fail just after the maneuver has been performed! This is a real case that has been encountered during validation ...

    Author:
    Luc Maisonobe
    See Also:
    Propagator.addEventDetector(EventDetector)
    • Constructor Detail

      • NodeDetector

        public NodeDetector​(Orbit orbit,
                            Frame frame)
        Build a new instance.

        The orbit is used only to set an upper bound for the max check interval to a value related to nodes separation (as computed by a Keplerian model) and to set the convergence threshold according to orbit size.

        Parameters:
        orbit - initial orbit
        frame - frame in which the equator is defined (typical values are EME2000 or ITRF)
      • NodeDetector

        public NodeDetector​(double threshold,
                            Orbit orbit,
                            Frame frame)
        Build a new instance.

        The orbit is used only to set an upper bound for the max check interval to a value related to nodes separation (as computed by a Keplerian model).

        Parameters:
        threshold - convergence threshold (s)
        orbit - initial orbit
        frame - frame in which the equator is defined (typical values are EME2000 or ITRF)
      • NodeDetector

        protected NodeDetector​(AdaptableInterval maxCheck,
                               double threshold,
                               int maxIter,
                               EventHandler handler,
                               Frame frame)
        Protected constructor with full parameters.

        This constructor is not public as users are expected to use the builder API with the various withXxx() methods to set up the instance in a readable manner without using a huge amount of parameters.

        Parameters:
        maxCheck - maximum checking interval
        threshold - convergence threshold (s)
        maxIter - maximum number of iterations in the event time search
        handler - event handler to call at event occurrences
        frame - frame in which the equator is defined (typical values are EME2000 or ITRF)
        Since:
        6.1
    • Method Detail

      • create

        protected NodeDetector create​(AdaptableInterval newMaxCheck,
                                      double newThreshold,
                                      int newMaxIter,
                                      EventHandler newHandler)
        Build a new instance.
        Specified by:
        create in class AbstractDetector<NodeDetector>
        Parameters:
        newMaxCheck - maximum checking interval (s)
        newThreshold - convergence threshold (s)
        newMaxIter - maximum number of iterations in the event time search
        newHandler - event handler to call at event occurrences
        Returns:
        a new instance of the appropriate sub-type
      • getFrame

        public Frame getFrame()
        Get the frame in which the equator is defined.
        Returns:
        the frame in which the equator is defined
      • g

        public double g​(SpacecraftState s)
        Compute the value of the switching function. This function computes the Z position in the defined frame.
        Specified by:
        g in interface EventDetector
        Specified by:
        g in class AbstractDetector<NodeDetector>
        Parameters:
        s - the current state information: date, kinematics, attitude
        Returns:
        value of the switching function