org.orekit.propagation.events
Class AltitudeDetector

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

All Implemented Interfaces:

java.io.Serializable, EventDetector

public class AltitudeDetector
extends AbstractDetector

Finder for satellite altitude crossing events.

This class finds altitude events (i.e. satellite crossing a predefined altitude level above ground).

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

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

AltitudeDetector(double altitude, BodyShape bodyShape)
Build a new altitude detector.

AltitudeDetector(double maxCheck, double altitude, BodyShape bodyShape)
Build a new altitude detector.

AltitudeDetector(double maxCheck, double threshold, double altitude, BodyShape bodyShape)
Build a new altitude detector.

Method Summary

int	eventOccurred(SpacecraftState s, boolean increasing) Handle an altitude event and choose what to do next.
double	g(SpacecraftState s) Compute the value of the switching function.
double	getAltitude() Get the threshold altitude value.
BodyShape	getBodyShape() Get the body shape.

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

AltitudeDetector

public AltitudeDetector(double altitude,
                        BodyShape bodyShape)

Build a new altitude detector.

This simple constructor takes default values for maximal checking interval (AbstractDetector.DEFAULT_MAXCHECK) and convergence threshold (AbstractDetector.DEFAULT_THRESHOLD).

Parameters:

altitude - threshold altitude value

bodyShape - body shape with respect to which altitude should be evaluated

AltitudeDetector

public AltitudeDetector(double maxCheck,
                        double altitude,
                        BodyShape bodyShape)

Build a new altitude detector.

This simple constructor takes default value for convergence threshold (AbstractDetector.DEFAULT_THRESHOLD).

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

Parameters:

maxCheck - maximal checking interval (s)

altitude - threshold altitude value (m)

bodyShape - body shape with respect to which altitude should be evaluated

AltitudeDetector

public AltitudeDetector(double maxCheck,
                        double threshold,
                        double altitude,
                        BodyShape bodyShape)

Build a new altitude detector.

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

Parameters:

maxCheck - maximal checking interval (s)

threshold - convergence threshold (s)

altitude - threshold altitude value (m)

bodyShape - body shape with respect to which altitude should be evaluated

Method Detail

getAltitude

public double getAltitude()

Get the threshold altitude value.

Returns:

the threshold altitude value (m)

getBodyShape

public BodyShape getBodyShape()

Get the body shape.

Returns:

the body shape

eventOccurred

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

Handle an altitude event and choose what to do next.

The default implementation behavior is to continue propagation when ascending and to stop propagationwhen descending.

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 current altitude and the threshold altitude.

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