org.orekit.propagation.events
Class CircularFieldOfViewDetector

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

All Implemented Interfaces:

java.io.Serializable, EventDetector

public class CircularFieldOfViewDetector
extends AbstractDetector

Finder for target entry/exit events with respect to a satellite sensor field of view.

This class handle fields of view with a circular boundary.

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

Version:

$Revision$ $Date$

Author:

Véronique Pommier-Maurussane

See Also:

Propagator.addEventDetector(EventDetector), DihedralFieldOfViewDetector, 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

CircularFieldOfViewDetector(double maxCheck, PVCoordinatesProvider pvTarget, org.apache.commons.math.geometry.Vector3D center, double halfAperture)
Build a new instance.

Method Summary

int	eventOccurred(SpacecraftState s, boolean increasing) Handle an fov event and choose what to do next.
double	g(SpacecraftState s) Compute the value of the switching function.
org.apache.commons.math.geometry.Vector3D	getCenter() Get the direction of fov center.
double	getHalfAperture() Get fov half aperture angle.
PVCoordinatesProvider	getPVTarget() Get the position/velocity provider of the target .

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

CircularFieldOfViewDetector

public CircularFieldOfViewDetector(double maxCheck,
                                   PVCoordinatesProvider pvTarget,
                                   org.apache.commons.math.geometry.Vector3D center,
                                   double halfAperture)

Build a new instance.

The maximal interval between distance to fov boundary checks should be smaller than the half duration of the minimal pass to handle, otherwise some short passes could be missed.

Parameters:

maxCheck - maximal interval in seconds

pvTarget - Position/velocity provider of the considered target

center - Direction of the fov center, in spacecraft frame

halfAperture - Fov half aperture angle

Method Detail

getPVTarget

public PVCoordinatesProvider getPVTarget()

Get the position/velocity provider of the target .

Returns:

the position/velocity provider of the target

getCenter

public org.apache.commons.math.geometry.Vector3D getCenter()

Get the direction of fov center.

Returns:

the direction of fov center

getHalfAperture

public double getHalfAperture()

Get fov half aperture angle.

Returns:

the fov half aperture angle

eventOccurred

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

Handle an fov event and choose what to do next.

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

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, i.e. target enters the fov (note that increase is measured with respect to physical time, not with respect to propagation which may go backward in time)

Returns:

one of EventDetector.STOP, EventDetector.RESET_STATE, EventDetector.RESET_DERIVATIVES 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 must be continuous (at least in its roots neighborhood), as the integrator will need to find its roots to locate the events. g function value is the difference between fov half aperture and the absolute value of the angle between target direction and field of view center. It is positive inside the fov and negative outside.

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