org.orekit.propagation.events
Class ApsideDetector

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

All Implemented Interfaces:

java.io.Serializable, EventDetector

public class ApsideDetector
extends AbstractDetector

Finder for apside crossing events.

This class finds apside crossing events (i.e. apogee or perigee crossing).

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

Beware that apside detection will fail for almost circular orbits. If for example an apside detector is used to trigger an ImpulseManeuver and the maneuver change the orbit shape to circular, then the detector may completely fail just after the maneuver has been performed!

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

ApsideDetector(double threshold, Orbit orbit)
Build a new instance.

ApsideDetector(Orbit orbit)
Build a new instance.

Method Summary

int	eventOccurred(SpacecraftState s, boolean increasing) Handle an apside crossing event and choose what to do next.
double	g(SpacecraftState s) Compute the value of the switching function.

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

ApsideDetector

public ApsideDetector(Orbit orbit)

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

ApsideDetector

public ApsideDetector(double threshold,
                      Orbit orbit)

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

Method Detail

eventOccurred

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

Handle an apside crossing event and choose what to do next.

The default implementation behavior is to continue propagation at apogee crossing and to stop propagation at perigee 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 dot product of the 2 vectors : position.velocity.

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