Package org.orekit.propagation.events

Class FieldEventSlopeFilter<D extends FieldEventDetector<T>,T extends CalculusFieldElement<T>>

java.lang.Object

org.orekit.propagation.events.FieldAbstractDetector<FieldEventSlopeFilter<D,T>,T>

org.orekit.propagation.events.FieldEventSlopeFilter<D,T>

Type Parameters:

D - type of the detector

T - type of the field elements

All Implemented Interfaces:

FieldEventDetector<T>

public class FieldEventSlopeFilter<D extends FieldEventDetector<T>,T extends CalculusFieldElement<T>>
extends FieldAbstractDetector<FieldEventSlopeFilter<D,T>,T>

Wrapper used to detect only increasing or decreasing events.

This class is heavily based on the class EventFilter from the Hipparchus library. The changes performed consist in replacing raw types (double and double arrays) with space dynamics types (FieldAbsoluteDate, FieldSpacecraftState).

General events are defined implicitly by a g function crossing zero. This function needs to be continuous in the event neighborhood, and its sign must remain consistent between events. This implies that during an orbit propagation, events triggered are alternately events for which the function increases from negative to positive values, and events for which the function decreases from positive to negative values.

Sometimes, users are only interested in one type of event (say increasing events for example) and not in the other type. 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 FieldPropagator 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 then see only the interesting events, i.e. either only increasing events or only decreasing events. The number of calls to the g function will also be reduced.

See Also:

FieldEventEnablingPredicateFilter

Field Summary

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

DEFAULT_MAX_ITER, DEFAULT_MAXCHECK, DEFAULT_THRESHOLD

Constructor Summary

Constructors

Modifier	Constructor	Description
	FieldEventSlopeFilter(D rawDetector, FilterType filter)	Wrap an event detector.
protected	FieldEventSlopeFilter(FieldAdaptableInterval<T> maxCheck, T threshold, int maxIter, FieldEventHandler<T> handler, D rawDetector, FilterType filter)	Protected constructor with full parameters.

Method Summary

Modifier and Type	Method	Description
protected FieldEventSlopeFilter<D,T>	create(FieldAdaptableInterval<T> newMaxCheck, T newThreshold, int newMaxIter, FieldEventHandler<T> newHandler)	Build a new instance.
T	g(FieldSpacecraftState<T> s)	Compute the value of the switching function.
D	getDetector()	Get the wrapped raw detector.
void	init(FieldSpacecraftState<T> s0, FieldAbsoluteDate<T> t)	Initialize event handler at the start of a propagation.

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

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

Methods inherited from class java.lang.Object

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

Constructor Detail

FieldEventSlopeFilter

public FieldEventSlopeFilter(D rawDetector,
                             FilterType filter)

Wrap an event detector.

Parameters:

rawDetector - event detector to wrap

filter - filter to use

FieldEventSlopeFilter

protected FieldEventSlopeFilter(FieldAdaptableInterval<T> maxCheck,
                                T threshold,
                                int maxIter,
                                FieldEventHandler<T> handler,
                                D rawDetector,
                                FilterType filter)

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

rawDetector - event detector to wrap

filter - filter to use

Method Detail

create

protected FieldEventSlopeFilter<D,T> create(FieldAdaptableInterval<T> newMaxCheck,
                                                  T newThreshold,
                                                  int newMaxIter,
                                                  FieldEventHandler<T> newHandler)

Build a new instance.

Specified by:

create in class FieldAbstractDetector<FieldEventSlopeFilter<D extends FieldEventDetector<T>,T extends CalculusFieldElement<T>>,T extends CalculusFieldElement<T>>

Parameters:

newMaxCheck - maximum checking interval

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 D getDetector()

Get the wrapped raw detector.

Returns:

the wrapped raw detector

init

public void init(FieldSpacecraftState<T> s0,
                 FieldAbsoluteDate<T> 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

Specified by:

init in interface FieldEventDetector<D extends FieldEventDetector<T>>

Overrides:

init in class FieldAbstractDetector<FieldEventSlopeFilter<D extends FieldEventDetector<T>,T extends CalculusFieldElement<T>>,T extends CalculusFieldElement<T>>

Parameters:

s0 - initial state

t - target time for the integration

g

public T g(FieldSpacecraftState<T> 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 FieldEventDetector<D extends FieldEventDetector<T>>

Specified by:

g in class FieldAbstractDetector<FieldEventSlopeFilter<D extends FieldEventDetector<T>,T extends CalculusFieldElement<T>>,T extends CalculusFieldElement<T>>

Parameters:

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

Returns:

value of the switching function