Package org.orekit.propagation.events

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

java.lang.Object

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 Object
implements FieldEventDetector<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

Constructor Summary

Constructors

Constructor	Description
FieldEventSlopeFilter(D rawDetector, FilterType filterType)	Wrap an event detector.
FieldEventSlopeFilter(FieldEventDetectionSettings<T> detectionSettings, D rawDetector, FilterType filterType)	Constructor with full parameters.

Method Summary

Modifier and Type	Method	Description
void	finish(FieldSpacecraftState<T> state)	This method finalizes the event detector's job.
T	g(FieldSpacecraftState<T> s)	Compute the value of the switching function.
FieldEventDetectionSettings<T>	getDetectionSettings()	Getter for the settings.
D	getDetector()	Get the wrapped raw detector.
EventFunction	getEventFunction()	Get the event function.
FilterType	getFilterType()	Get filter type.
FieldEventHandler<T>	getHandler()	Get the handler.
void	init(FieldSpacecraftState<T> s0, FieldAbsoluteDate<T> t)	Initialize event detector at the start of a propagation.
boolean	isForward()	Check if the current propagation is forward or backward.
void	reset(FieldSpacecraftState<T> state, FieldAbsoluteDate<T> target)	Reset the event detector during propagation when the state is modified by an event or an additional data provider.
FieldEventSlopeFilter<D,T>	withDetectionSettings(FieldEventDetectionSettings<T> settings)	Builds a new instance from the input detection settings.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.orekit.propagation.events.FieldEventDetector

getMaxCheckInterval, getMaxIterationCount, getThreshold

Constructor Details

FieldEventSlopeFilter

public FieldEventSlopeFilter(D rawDetector,
 FilterType filterType)

Wrap an event detector.

Parameters:

rawDetector - event detector to wrap

filterType - filter to use

FieldEventSlopeFilter

public FieldEventSlopeFilter(FieldEventDetectionSettings<T> detectionSettings,
 D rawDetector,
 FilterType filterType)

Constructor with full parameters.

Parameters:

detectionSettings - event detection settings

rawDetector - event detector to wrap

filterType - filter to use since 13.0

Method Details

withDetectionSettings

public FieldEventSlopeFilter<D,T> withDetectionSettings(FieldEventDetectionSettings<T> settings)

Builds a new instance from the input detection settings.

Parameters:

settings - event detection settings to be used

Returns:

a new detector

getFilterType

public FilterType getFilterType()

Get filter type.

Returns:

filter type

Since:

13.0

getEventFunction

public EventFunction getEventFunction()

Description copied from interface: FieldEventDetector

Get the event function. It defines g both for double and Field.

Specified by:

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

Returns:

event function

getHandler

public FieldEventHandler<T> getHandler()

Description copied from interface: FieldEventDetector

Get the handler.

Specified by:

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

Returns:

event handler to call at event occurrences

getDetectionSettings

public FieldEventDetectionSettings<T> getDetectionSettings()

Description copied from interface: FieldEventDetector

Getter for the settings.

Specified by:

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

Returns:

detection settings

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 detector at the start of a propagation.

This method is called once at the start of the propagation. It may be used by the event detector to initialize some internal data if needed.

The default implementation initializes the handler.

Specified by:

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

Parameters:

s0 - initial state

t - target time for the integration

reset

public void reset(FieldSpacecraftState<T> state,
 FieldAbsoluteDate<T> target)

Reset the event detector during propagation when the state is modified by an event or an additional data provider.

The default implementation does nothing.

Specified by:

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

Parameters:

state - current state

target - target time for the integration

finish

public void finish(FieldSpacecraftState<T> state)

This method finalizes the event detector's job.

Specified by:

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

Parameters:

state - state at propagation end

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>>

Parameters:

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

Returns:

value of the switching function

isForward

public boolean isForward()

Check if the current propagation is forward or backward.

Returns:

true if the current propagation is forward