Package org.orekit.propagation.events

Class FieldOfViewDetector

java.lang.Object

org.orekit.propagation.events.AbstractDetector<FieldOfViewDetector>

org.orekit.propagation.events.FieldOfViewDetector

All Implemented Interfaces:

EventDetector

public class FieldOfViewDetector
extends AbstractDetector<FieldOfViewDetector>

Finder for target entry/exit events with respect to a satellite sensor Field Of View.

Beware that this detector is unaware of any bodies occluding line-of-sight to the target. It can be therefore used for many contexts from Earth Observation to interplanetary mission design. For instance, in an Earth Observation context, it can be easily combined to an ElevationDetector using BooleanDetector.andCombine(java.util.Collection) to calculate station visibility opportunities within the satellite's field of view.

The default implementation behavior is to continue propagation at FOV entry and to stop propagation at FOV exit. This can be changed by calling AbstractDetector.withHandler(EventHandler) after construction.

Since:

7.1

Author:

Luc Maisonobe

See Also:

Propagator.addEventDetector(EventDetector), FootprintOverlapDetector, VisibilityTrigger

Field Summary

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

DEFAULT_MAX_ITER, DEFAULT_MAXCHECK, DEFAULT_THRESHOLD

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	FieldOfViewDetector(AdaptableInterval maxCheck, double threshold, int maxIter, EventHandler handler, PVCoordinatesProvider pvTarget, double radiusTarget, VisibilityTrigger trigger, FieldOfView fov)	Protected constructor with full parameters.
	FieldOfViewDetector(PVCoordinatesProvider pvTarget, double radiusTarget, VisibilityTrigger trigger, FieldOfView fov)	Build a new instance.
	FieldOfViewDetector(PVCoordinatesProvider pvTarget, FieldOfView fov)	Build a new instance.

Method Summary

Modifier and Type	Method	Description
protected FieldOfViewDetector	create(AdaptableInterval newMaxCheck, double newThreshold, int newMaxIter, EventHandler newHandler)	Build a new instance.
double	g(SpacecraftState s)	Compute the value of the switching function.
FieldOfView	getFOV()	Get the Field Of View.
PVCoordinatesProvider	getPVTarget()	Get the position/velocity provider of the target .

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

getHandler, getMaxCheckInterval, getMaxIterationCount, getThreshold, init, isForward, withHandler, withMaxCheck, withMaxCheck, withMaxIter, withThreshold

Methods inherited from class java.lang.Object

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

Constructor Detail

FieldOfViewDetector

public FieldOfViewDetector(PVCoordinatesProvider pvTarget,
                           FieldOfView fov)

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:

pvTarget - Position/velocity provider of the considered target

fov - Field Of View

Since:

10.1

FieldOfViewDetector

public FieldOfViewDetector(PVCoordinatesProvider pvTarget,
                           double radiusTarget,
                           VisibilityTrigger trigger,
                           FieldOfView fov)

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:

pvTarget - Position/velocity provider of the considered target

radiusTarget - radius of the target, considered to be a spherical body (m)

trigger - visibility trigger for spherical bodies

fov - Field Of View

Since:

10.1

FieldOfViewDetector

protected FieldOfViewDetector(AdaptableInterval maxCheck,
                              double threshold,
                              int maxIter,
                              EventHandler handler,
                              PVCoordinatesProvider pvTarget,
                              double radiusTarget,
                              VisibilityTrigger trigger,
                              FieldOfView fov)

Protected constructor with full parameters.

This constructor is not public as users are expected to use the builder API with the various withXxx() methods to set up the instance in a readable manner without using a huge amount of parameters.

Parameters:

maxCheck - maximum checking interval

threshold - convergence threshold (s)

maxIter - maximum number of iterations in the event time search

handler - event handler to call at event occurrences

pvTarget - Position/velocity provider of the considered target

radiusTarget - radius of the target, considered to be a spherical body (m)

trigger - visibility trigger for spherical bodies

fov - Field Of View

Method Detail

create

protected FieldOfViewDetector create(AdaptableInterval newMaxCheck,
                                     double newThreshold,
                                     int newMaxIter,
                                     EventHandler newHandler)

Build a new instance.

Specified by:

create in class AbstractDetector<FieldOfViewDetector>

Parameters:

newMaxCheck - maximum checking interval (s)

newThreshold - convergence threshold (s)

newMaxIter - maximum number of iterations in the event time search

newHandler - event handler to call at event occurrences

Returns:

a new instance of the appropriate sub-type

getPVTarget

public PVCoordinatesProvider getPVTarget()

Get the position/velocity provider of the target .

Returns:

the position/velocity provider of the target

getFOV

public FieldOfView getFOV()

Get the Field Of View.

Returns:

Field Of View

Since:

10.1

g

public double g(SpacecraftState s)

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.

The g function value is the angular offset between the target center and the Field Of View boundary, plus or minus the target angular radius depending on the VisibilityTrigger, minus the Field Of View margin. It is therefore negative if the target is visible within the Field Of View and positive if it is outside of the Field Of View.

As per the previous definition, when the target enters the Field Of View, a decreasing event is generated, and when the target leaves the Field Of View, an increasing event is generated.

Specified by:

g in interface EventDetector

Specified by:

g in class AbstractDetector<FieldOfViewDetector>

Parameters:

s - the current state information: date, kinematics, attitude

Returns:

value of the switching function