org.orekit.propagation.events
Class NodeDetector

java.lang.Object
  org.orekit.propagation.events.AbstractDetector
      org.orekit.propagation.events.NodeDetector

All Implemented Interfaces:

java.io.Serializable, EventDetector

public class NodeDetector
extends AbstractDetector

Finder for node crossing events.

This class finds equator crossing events (i.e. ascending or descending node crossing).

The default implementation behavior is to continue propagation at descending node crossing and to stop propagation at ascending node crossing. This can be changed by overriding the eventOccurred method in a derived class.

Beware that node detection will fail for almost equatorial orbits. If for example a node detector is used to trigger an ImpulseManeuver and the maneuver turn the orbit plane to equator, then the detector may completely fail just after the maneuver has been performed! This is a real case that has been encountered during validation ...

Version:

$Revision: 3027 $ $Date: 2010-01-19 11:36:25 +0100 (mar. 19 janv. 2010) $

Author:

Luc Maisonobe

See Also:

Propagator.addEventDetector(EventDetector), Serialized Form

Field Summary

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

DEFAULT_MAXCHECK, DEFAULT_THRESHOLD

Fields inherited from interface org.orekit.propagation.events.EventDetector

CONTINUE, RESET_DERIVATIVES, RESET_STATE, STOP

Constructor Summary

NodeDetector(double threshold, Orbit orbit, Frame frame)
Build a new instance.

NodeDetector(Orbit orbit, Frame frame)
Build a new instance.

Method Summary

int	eventOccurred(SpacecraftState s, boolean increasing) Handle a node crossing event and choose what to do next.
double	g(SpacecraftState s) Compute the value of the switching function.
Frame	getFrame() Get the frame in which the equator is defined.

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

getMaxCheckInterval, getMaxIterationCount, getThreshold, resetState

Methods inherited from class java.lang.Object

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

Constructor Detail

NodeDetector

public NodeDetector(Orbit orbit,
                    Frame frame)

Build a new instance.

The orbit is used only to set an upper bound for the max check interval to period/3 and to set the convergence threshold according to orbit size.

Parameters:

orbit - initial orbit

frame - frame in which the equator is defined (typical values are J2000 or ITRF 2005)

NodeDetector

public NodeDetector(double threshold,
                    Orbit orbit,
                    Frame frame)

Build a new instance.

The orbit is used only to set an upper bound for the max check interval to period/3.

Parameters:

threshold - convergence threshold (s)

orbit - initial orbit

frame - frame in which the equator is defined (typical values are J2000 or ITRF 2005)

Method Detail

getFrame

public Frame getFrame()

Get the frame in which the equator is defined.

Returns:

the frame in which the equator is defined

eventOccurred

public int eventOccurred(SpacecraftState s,
                         boolean increasing)
                  throws OrekitException

Handle a node crossing event and choose what to do next.

The default implementation behavior is to continue propagation at descending node crossing and to stop propagation at ascending node crossing.

Specified by:

eventOccurred in interface EventDetector

Specified by:

eventOccurred in class AbstractDetector

Parameters:

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

increasing - if true, the value of the switching function increases when times increases around event

Returns:

EventDetector.STOP or EventDetector.CONTINUE

Throws:

OrekitException - if some specific error occurs

g

public double g(SpacecraftState s)
         throws OrekitException

Compute the value of the switching function. This function computes the Z position in the defined frame.

Specified by:

g in interface EventDetector

Specified by:

g in class AbstractDetector

Parameters:

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

Returns:

value of the switching function

Throws:

OrekitException - if some specific error occurs