org.orekit.propagation.events
Class GroundMaskElevationDetector

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

All Implemented Interfaces:

Serializable, EventDetector

public class GroundMaskElevationDetector
extends AbstractDetector

Finder for satellite azimuth-elevation events with respect to a mask.

This class finds elevation events (i.e. satellite raising and setting) with respect to an azimuth-elevation mask.

An azimuth-elevation mask defines the physical horizon for a local point, origin of some topocentric frame.

Azimuth is defined according to getAzimuth. Elevation is defined according to getElevation.

The azimuth elevation mask must be supplied as a twodimensional array with multiples lines of pairs of azimuth-elevation angles. First row will be filled with azimuth values, second row with elevation values, as in the following snippet:

    double [][] mask = {
                        {FastMathFastMath.toRadians(0),   FastMath.toRadians(10)},
                        {FastMathFastMath.toRadians(45),  FastMath.toRadians(8)},
                        {FastMathFastMath.toRadians(90),  FastMath.toRadians(6)},
                        {FastMathFastMath.toRadians(135), FastMath.toRadians(4)},
                        {FastMathFastMath.toRadians(180), FastMath.toRadians(5)},
                        {FastMathFastMath.toRadians(225), FastMath.toRadians(6)},
                        {FastMathFastMath.toRadians(270), FastMath.toRadians(8)},
                        {FastMathFastMath.toRadians(315), FastMath.toRadians(9)}
                       };
  

No assumption is made on azimuth values and ordering. The only restraint is that only one elevation value can be associated to identical azimuths modulo 2PI.

The default implementation behavior is to continue propagation at raising and to stop propagation at setting. This can be changed by using provided constructors.

Author:

Pascal Parraud

See Also:

Propagator.addEventDetector(EventDetector), Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface org.orekit.propagation.events.EventDetector

EventDetector.Action

Field Summary

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

DEFAULT_MAXCHECK, DEFAULT_THRESHOLD

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

DECREASING, INCREASING, INCREASING_DECREASING

Constructor Summary

GroundMaskElevationDetector(double[][] azimelev, TopocentricFrame topo)
Build a new azimuth-elevation detector.

GroundMaskElevationDetector(double[][] azimelev, TopocentricFrame topo, double maxCheck)
Build a new azimuth-elevation detector.

GroundMaskElevationDetector(double[][] azimelev, TopocentricFrame topo, double maxCheck, double threshold)
Build a new azimuth-elevation detector.

GroundMaskElevationDetector(double[][] azimelev, TopocentricFrame topo, double maxCheck, double threshold, EventDetector.Action raising, EventDetector.Action setting)
Build a new azimuth-elevation detector.

GroundMaskElevationDetector(double[][] azimelev, TopocentricFrame topo, double maxCheck, double threshold, EventDetector.Action raising, EventDetector.Action setting, boolean removeRaising, boolean removeSetting)
Build a new azimuth-elevation detector.

Method Summary

EventDetector.Action	eventOccurred(SpacecraftState s, boolean increasing, boolean forward) Handle an azimuth-elevation event and choose what to do next.
double	g(SpacecraftState s) Compute the value of the switching function.
double	getElevation(double azimuth) Get the interpolated elevation for a given azimuth according to the mask.
TopocentricFrame	getTopocentricFrame() Get the topocentric frame.
boolean	shouldBeRemoved() This method is called after EventDetector.eventOccurred(org.orekit.propagation.SpacecraftState, boolean, boolean) has been triggered.

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

getMaxCheckInterval, getMaxIterationCount, getSlopeSelection, getThreshold, init, resetState

Methods inherited from class java.lang.Object

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

Constructor Detail

GroundMaskElevationDetector

public GroundMaskElevationDetector(double[][] azimelev,
                                   TopocentricFrame topo)

Build a new azimuth-elevation detector.

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

Parameters:

azimelev - azimuth-elevation mask (rad)

topo - topocentric frame in which elevation should be evaluated

Throws:

IllegalArgumentException - if azimuth-elevation mask is not supported

GroundMaskElevationDetector

public GroundMaskElevationDetector(double[][] azimelev,
                                   TopocentricFrame topo,
                                   double maxCheck)

Build a new azimuth-elevation detector.

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

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

Parameters:

azimelev - azimuth-elevation mask (rad)

topo - topocentric frame in which elevation should be evaluated

maxCheck - maximal checking interval (s)

Throws:

IllegalArgumentException - if azimuth-elevation mask is not supported

GroundMaskElevationDetector

public GroundMaskElevationDetector(double[][] azimelev,
                                   TopocentricFrame topo,
                                   double maxCheck,
                                   double threshold)

Build a new azimuth-elevation detector.

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

The default implementation behavior is to continue propagation at raising and to stop propagation at setting.

Parameters:

azimelev - azimuth-elevation mask (rad)

topo - topocentric frame in which elevation should be evaluated

maxCheck - maximal checking interval (s)

threshold - convergence threshold (s)

Throws:

IllegalArgumentException - if azimuth-elevation mask is not supported

GroundMaskElevationDetector

public GroundMaskElevationDetector(double[][] azimelev,
                                   TopocentricFrame topo,
                                   double maxCheck,
                                   double threshold,
                                   EventDetector.Action raising,
                                   EventDetector.Action setting)

Build a new azimuth-elevation detector.

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

Parameters:

azimelev - azimuth-elevation mask (rad)

topo - topocentric frame in which elevation should be evaluated

maxCheck - maximal checking interval (s)

threshold - convergence threshold (s)

raising - action performed when propagation at raising

setting - action performed when propagation at setting

Throws:

IllegalArgumentException - if azimuth-elevation mask is not supported

GroundMaskElevationDetector

public GroundMaskElevationDetector(double[][] azimelev,
                                   TopocentricFrame topo,
                                   double maxCheck,
                                   double threshold,
                                   EventDetector.Action raising,
                                   EventDetector.Action setting,
                                   boolean removeRaising,
                                   boolean removeSetting)

Build a new azimuth-elevation detector.

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

Parameters:

azimelev - azimuth-elevation mask (rad)

topo - topocentric frame in which elevation should be evaluated

maxCheck - maximal checking interval (s)

threshold - convergence threshold (s)

raising - action performed when propagation at raising

setting - action performed when propagation at setting

removeRaising - if detector should be removed at raising

removeSetting - if detector should be removed at setting

Throws:

IllegalArgumentException - if azimuth-elevation mask is not supported

Method Detail

getTopocentricFrame

public TopocentricFrame getTopocentricFrame()

Get the topocentric frame.

Returns:

the topocentric frame

eventOccurred

public EventDetector.Action eventOccurred(SpacecraftState s,
                                          boolean increasing,
                                          boolean forward)
                                   throws OrekitException

Handle an azimuth-elevation event and choose what to do next.

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

forward - if true, the integration variable (time) increases during integration.

Returns:

the action performed when propagation raising or setting.

Throws:

OrekitException - if some specific error occurs

shouldBeRemoved

public boolean shouldBeRemoved()

This method is called after EventDetector.eventOccurred(org.orekit.propagation.SpacecraftState, boolean, boolean) has been triggered. It returns true if the current detector should be removed after first event detection. WARNING: this method can be called only once a event has been triggered. Before, the value is not available.

Specified by:

shouldBeRemoved in interface EventDetector

Specified by:

shouldBeRemoved in class AbstractDetector

Returns:

true if the current detector should be removed after first event detection

g

public double g(SpacecraftState s)
         throws OrekitException

Compute the value of the switching function. This function measures the difference between the current elevation and the elevation for current azimuth interpolated from azimuth-elevation mask.

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

getElevation

public double getElevation(double azimuth)

Get the interpolated elevation for a given azimuth according to the mask.

Parameters:

azimuth - azimuth (rad)

Returns:

elevation angle (rad)