Package org.orekit.propagation.events

Class EventEnablingPredicateFilter<T extends EventDetector>

java.lang.Object

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

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

All Implemented Interfaces:

Serializable, EventDetector

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

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, 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
EventEnablingPredicateFilter(T rawDetector, EnablingPredicate<? super T> enabler)	Wrap an event detector.

Method Summary

Modifier and Type	Method	Description
protected EventEnablingPredicateFilter<T>	create(double newMaxCheck, double newThreshold, int newMaxIter, EventHandler<? super EventEnablingPredicateFilter<T>> newHandler)	Build a new instance.
double	g(SpacecraftState s)	Compute the value of the switching function.
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

EventEnablingPredicateFilter

public EventEnablingPredicateFilter(T rawDetector,
                                    EnablingPredicate<? super T> enabler)

Wrap an event detector.

Parameters:

rawDetector - event detector to wrap

enabler - event enabling predicate function to use

Method Detail

create

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

Build a new instance.

Specified by:

create in class AbstractDetector<EventEnablingPredicateFilter<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

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<EventEnablingPredicateFilter<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<EventEnablingPredicateFilter<T extends EventDetector>>

Parameters:

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

Returns:

value of the switching function