org.orekit.propagation.events

Interface EventDetector

All Superinterfaces:

Serializable

All Known Implementing Classes:

AbstractDetector, AlignmentDetector, AltitudeDetector, ApsideDetector, CircularFieldOfViewDetector, DateDetector, DihedralFieldOfViewDetector, EclipseDetector, ElevationDetector, EventFilter, EventShifter, GeographicZoneDetector, ImpulseManeuver, NodeDetector

public interface EventDetector
extends Serializable

This interface represents space-dynamics aware events detectors.

It mirrors the EventHandler interface from Apache Commons Math but provides a space-dynamics interface to the methods.

Events detectors are a useful solution to meet the requirements of propagators concerning discrete conditions. The state of each event detector is queried by the integrator at each step. When the sign of the underlying g switching function changes, the step is rejected and reduced, in order to make sure the sign changes occur only at steps boundaries.

When step ends exactly at a switching function sign change, the corresponding event is triggered, by calling the eventOccurred(SpacecraftState, boolean) method. The method can do whatever it needs with the event (logging it, performing some processing, ignore it ...). The return value of the method will be used by the propagator to stop or resume propagation, possibly changing the state vector.

Author:

Luc Maisonobe, Véronique Pommier-Maurussane

Method Summary

Methods

Modifier and Type	Method and Description
EventHandler.Action	eventOccurred(SpacecraftState s, boolean increasing) Handle the event.
double	g(SpacecraftState s) Compute the value of the switching function.
double	getMaxCheckInterval() Get maximal time interval between switching function checks.
int	getMaxIterationCount() Get maximal number of iterations in the event time search.
double	getThreshold() Get the convergence threshold in the event time search.
void	init(SpacecraftState s0, AbsoluteDate t) Initialize event handler at the start of a propagation.
SpacecraftState	resetState(SpacecraftState oldState) Reset the state prior to continue propagation.

Method Detail

init

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.

Parameters:

s0 - initial state

t - target time for the integration

g

double g(SpacecraftState s)
         throws OrekitException

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.

Parameters:

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

Returns:

value of the switching function

Throws:

OrekitException - if some specific error occurs

getThreshold

double getThreshold()

Get the convergence threshold in the event time search.

Returns:

convergence threshold (s)

getMaxCheckInterval

double getMaxCheckInterval()

Get maximal time interval between switching function checks.

Returns:

maximal time interval (s) between switching function checks

getMaxIterationCount

int getMaxIterationCount()

Get maximal number of iterations in the event time search.

Returns:

maximal number of iterations in the event time search

eventOccurred

EventHandler.Action eventOccurred(SpacecraftState s,
                                boolean increasing)
                                  throws OrekitException

Handle the event.

Parameters:

s - SpaceCraft state to be used in the evaluation

increasing - with the event occured in an "increasing" or "decreasing" slope direction

Returns:

the Action that the calling detector should pass back to the evaluation system

Throws:

OrekitException - if some specific error occurs

Since:

7.0

resetState

SpacecraftState resetState(SpacecraftState oldState)
                           throws OrekitException

Reset the state prior to continue propagation.

This method is called after the step handler has returned and before the next step is started, but only when eventOccurred(org.orekit.propagation.SpacecraftState, boolean) has itself returned the EventHandler.Action.RESET_STATE indicator. It allows the user to reset the state for the next step, without perturbing the step handler of the finishing step. If the eventOccurred(org.orekit.propagation.SpacecraftState, boolean) never returns the EventHandler.Action.RESET_STATE indicator, this function will never be called, and it is safe to simply return null.

Parameters:

oldState - old state

Returns:

new state

Throws:

OrekitException - if the state cannot be reseted

Since:

7.0