org.orekit.propagation.events
Class AlignmentDetector

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

All Implemented Interfaces:

java.io.Serializable, EventDetector

public class AlignmentDetector
extends AbstractDetector

Finder for satellite/body alignment events.

This class finds alignment events.

Alignment means the conjunction, with some threshold angle, between the satellite position and the projection in the orbital plane of some body position.

The default implementation behavior is to stop propagation when alignment is reached. This can be changed by overriding the eventOccurred method in a derived class.

Version:

$Revision: 3143 $ $Date: 2010-02-19 17:25:34 +0100 (ven. 19 févr. 2010) $

Author:

Pascal Parraud

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

AlignmentDetector(double threshold, Orbit orbit, PVCoordinatesProvider body, double alignAngle)
Build a new alignment detector.

AlignmentDetector(Orbit orbit, PVCoordinatesProvider body, double alignAngle)
Build a new alignment detector.

Method Summary

int	eventOccurred(SpacecraftState s, boolean increasing) Handle an alignment event and choose what to do next.
double	g(SpacecraftState s) Compute the value of the switching function.
double	getAlignAngle() Get the alignment angle (rad).
PVCoordinatesProvider	getPVCoordinatesProvider() Get the body to align.

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

AlignmentDetector

public AlignmentDetector(Orbit orbit,
                         PVCoordinatesProvider body,
                         double alignAngle)

Build a new alignment detector.

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

body - the body to align

alignAngle - the alignment angle (rad)

AlignmentDetector

public AlignmentDetector(double threshold,
                         Orbit orbit,
                         PVCoordinatesProvider body,
                         double alignAngle)

Build a new alignment detector.

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

body - the body to align

alignAngle - the alignment angle (rad)

Method Detail

getPVCoordinatesProvider

public PVCoordinatesProvider getPVCoordinatesProvider()

Get the body to align.

Returns:

the body to align

getAlignAngle

public double getAlignAngle()

Get the alignment angle (rad).

Returns:

the alignment angle

eventOccurred

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

Handle an alignment event and choose what to do next.

The default implementation behavior is to stop propagation when alignment is reached.

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 measures the difference between the alignment angle and the angle between the satellite position and the body position projection in the orbital plane.

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