Package org.orekit.propagation.events

Class EventShifter<T extends EventDetector>

java.lang.Object

org.orekit.propagation.events.AbstractDetector<EventShifter<T>>

org.orekit.propagation.events.EventShifter<T>

Type Parameters:

T - class type for the generic version

All Implemented Interfaces:

Serializable, EventDetector

public class EventShifter<T extends EventDetector>
extends AbstractDetector<EventShifter<T>>

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, Serialized Form

Field Summary

Fields inherited from class org.orekit.propagation.events.AbstractDetector

DEFAULT_MAX_ITER, DEFAULT_MAXCHECK, DEFAULT_THRESHOLD

Constructor Summary

Constructors

Constructor	Description
EventShifter(T detector, boolean useShiftedStates, double increasingTimeShift, double decreasingTimeShift)	Build a new instance.

Method Summary

Modifier and Type	Method	Description
protected EventShifter<T>	create(double newMaxCheck, double newThreshold, int newMaxIter, EventHandler<? super EventShifter<T>> newHandler)	Build a new instance.
double	g(SpacecraftState s)	Compute the value of the switching function.
double	getDecreasingTimeShift()	Get the decreasing events time shift.
double	getIncreasingTimeShift()	Get the increasing events time shift.
void	init(SpacecraftState s0, AbsoluteDate t)	Initialize event handler at the start of a propagation.

Methods inherited from class org.orekit.propagation.events.AbstractDetector

eventOccurred, getHandler, getMaxCheckInterval, getMaxIterationCount, getThreshold, isForward, resetState, withHandler, withMaxCheck, withMaxIter, withThreshold

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

EventShifter

public EventShifter(T 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 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.

Method Detail

create

protected EventShifter<T> create(double newMaxCheck,
                                 double newThreshold,
                                 int newMaxIter,
                                 EventHandler<? super EventShifter<T>> newHandler)

Build a new instance.

Specified by:

create in class AbstractDetector<EventShifter<T extends EventDetector>>

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

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<T extends EventDetector>>

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<T extends EventDetector>>

Parameters:

s - the current state information: date, kinematics, attitude

Returns:

value of the switching function