Package org.orekit.propagation.events

Class EventShifter

  • All Implemented Interfaces:
    EventDetector
    public class EventShifter
extends AbstractDetector<EventShifter>
    Wrapper shifting events occurrences times.

    This class wraps an event detector to slightly shift the events occurrences times. A typical use case is for handling operational delays before or after some physical event really occurs.

    For example, the satellite attitude mode may be switched from sun pointed to spin-stabilized a few minutes before eclipse entry, and switched back to sun pointed a few minutes after eclipse exit. This behavior is handled by wrapping an eclipse detector into an instance of this class with a positive times shift for increasing events (eclipse exit) and a negative times shift for decreasing events (eclipse entry).

    Author:
    Luc Maisonobe
    See Also:
    Propagator.addEventDetector(EventDetector), EventDetector

    • Constructor Detail

      • EventShifter

        public EventShifter​(EventDetector detector,
                    boolean useShiftedStates,
                    double increasingTimeShift,
                    double decreasingTimeShift)
        Build a new instance.

        The max check interval, the convergence threshold of the raw unshifted events will be used for the shifted event. When an event occurs, the eventOccurred method of the raw unshifted events will be called (with spacecraft state at either the shifted or the unshifted event date depending on the useShiftedStates parameter).

        Parameters:
        detector - event detector for the raw unshifted event
        useShiftedStates - if true, the state provided to eventOccurred method of the associated handler will remain shifted, otherwise it will be unshifted to correspond to the underlying raw event.
        increasingTimeShift - increasing events time shift.
        decreasingTimeShift - decreasing events time shift.

      • EventShifter

        protected EventShifter​(AdaptableInterval maxCheck,
                       double threshold,
                       int maxIter,
                       EventHandler handler,
                       EventDetector detector,
                       boolean useShiftedStates,
                       double increasingTimeShift,
                       double decreasingTimeShift)
        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
        detector - event detector for the raw unshifted event
        useShiftedStates - if true, the state provided to eventOccurred method of the detector will remain shifted, otherwise it will be unshifted to correspond to the underlying raw event.
        increasingTimeShift - increasing events time shift.
        decreasingTimeShift - decreasing events time shift.
        Since:
        6.1

    • Method Detail

      • create

        protected EventShifter create​(AdaptableInterval newMaxCheck,
                              double newThreshold,
                              int newMaxIter,
                              EventHandler newHandler)
        Build a new instance.
        Specified by:
        create in class AbstractDetector<EventShifter>
        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

      • getDetector

        public EventDetector getDetector()
        Get the detector for the raw unshifted event.
        Returns:
        the detector for the raw unshifted event
        Since:
        11.1

      • getIncreasingTimeShift

        public double getIncreasingTimeShift()
        Get the increasing events time shift.
        Returns:
        increasing events time shift

      • getDecreasingTimeShift

        public double getDecreasingTimeShift()
        Get the decreasing events time shift.
        Returns:
        decreasing events time shift

      • init

        public void init​(SpacecraftState s0,
                 AbsoluteDate t)
        Initialize event handler 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 does nothing

        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<EventShifter>
        Parameters:
        s0 - initial state
        t - 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 EventDetector
        Specified by:
        g in class AbstractDetector<EventShifter>
        Parameters:
        s - the current state information: date, kinematics, attitude
        Returns:
        value of the switching function