Package org.orekit.propagation.events

Class GroundAtNightDetector

java.lang.Object

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

org.orekit.propagation.events.AbstractTopocentricDetector<GroundAtNightDetector>

org.orekit.propagation.events.GroundAtNightDetector

All Implemented Interfaces:

EventDetector

public class GroundAtNightDetector
extends AbstractTopocentricDetector<GroundAtNightDetector>

Detector for ground location being at night.

This detector is mainly useful for scheduling optical measurements (either passive telescope observation of satellites against the stars background or active satellite laser ranging).

The g function of this detector is positive when ground is at night (i.e. Sun is below dawn/dusk elevation angle).

Since:

9.3

Author:

Luc Maisonobe

Field Summary

Fields

Modifier and Type	Field	Description
static final double	ASTRONOMICAL_DAWN_DUSK_ELEVATION	Sun elevation at astronomical dawn/dusk (18° below horizon).
static final double	CIVIL_DAWN_DUSK_ELEVATION	Sun elevation at civil dawn/dusk (6° below horizon).
static final double	NAUTICAL_DAWN_DUSK_ELEVATION	Sun elevation at nautical dawn/dusk (12° below horizon).

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

DEFAULT_MAX_CHECK, DEFAULT_MAX_ITER, DEFAULT_THRESHOLD

Constructor Summary

Constructors

Modifier	Constructor	Description
	GroundAtNightDetector(TopocentricFrame groundLocation, PVCoordinatesProvider sun, double dawnDuskElevation, AtmosphericRefractionModel refractionModel)	Simple constructor.
	GroundAtNightDetector(GroundAtNightEventFunction groundAtNightEventFunction)	Constructor from event function.
protected	GroundAtNightDetector(GroundAtNightEventFunction groundAtNightEventFunction, EventDetectionSettings detectionSettings, EventHandler handler)	Protected constructor.

Method Summary

Modifier and Type	Method	Description
protected GroundAtNightDetector	create(EventDetectionSettings detectionSettings, EventHandler newHandler)	Build a new instance.
double	g(SpacecraftState state)	Compute the value of the switching function.

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

getElevation, getTopocentricFrame

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

checkIfForward, getDetectionSettings, getEventFunction, getHandler, init, isForward, withDetectionSettings, withHandler, withMaxCheck, withMaxCheck, withMaxIter, withThreshold

Methods inherited from class java.lang.Object

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

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

finish, getMaxCheckInterval, getMaxIterationCount, getThreshold, reset

Field Details

CIVIL_DAWN_DUSK_ELEVATION

public static final double CIVIL_DAWN_DUSK_ELEVATION

Sun elevation at civil dawn/dusk (6° below horizon).

NAUTICAL_DAWN_DUSK_ELEVATION

public static final double NAUTICAL_DAWN_DUSK_ELEVATION

Sun elevation at nautical dawn/dusk (12° below horizon).

ASTRONOMICAL_DAWN_DUSK_ELEVATION

public static final double ASTRONOMICAL_DAWN_DUSK_ELEVATION

Sun elevation at astronomical dawn/dusk (18° below horizon).

Constructor Details

GroundAtNightDetector

public GroundAtNightDetector(TopocentricFrame groundLocation,
 PVCoordinatesProvider sun,
 double dawnDuskElevation,
 AtmosphericRefractionModel refractionModel)

Simple constructor.

Beware that Earth standard refraction model does apply only for elevations above -2°. It is therefore not suitable for used with CIVIL_DAWN_DUSK_ELEVATION (-6°), NAUTICAL_DAWN_DUSK_ELEVATION (-12°) or ASTRONOMICAL_DAWN_DUSK_ELEVATION (-18°). The ITU-R P.834 refraction model which can compute refraction at large negative elevations should be preferred.

Parameters:

groundLocation - ground location to check

sun - provider for Sun position

dawnDuskElevation - Sun elevation below which we consider night is dark enough (rad) (typically ASTRONOMICAL_DAWN_DUSK_ELEVATION)

refractionModel - reference to refraction model (null if refraction should be ignored)

GroundAtNightDetector

public GroundAtNightDetector(GroundAtNightEventFunction groundAtNightEventFunction)

Constructor from event function.

Parameters:

groundAtNightEventFunction - event function

Since:

14.0

GroundAtNightDetector

protected GroundAtNightDetector(GroundAtNightEventFunction groundAtNightEventFunction,
 EventDetectionSettings detectionSettings,
 EventHandler handler)

Protected constructor.

Parameters:

groundAtNightEventFunction - event function

detectionSettings - event detection settings

handler - event handler to call at event occurrences

Since:

14.0

Method Details

create

protected GroundAtNightDetector create(EventDetectionSettings detectionSettings,
 EventHandler newHandler)

Build a new instance.

Specified by:

create in class AbstractDetector<GroundAtNightDetector>

Parameters:

detectionSettings - detection settings

newHandler - event handler to call at event occurrences

Returns:

a new instance of the appropriate sub-type

g

public double g(SpacecraftState state)

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 of this detector is positive when ground is at night (i.e. Sun is below dawn/dusk elevation angle).

This function only depends on date, not on the actual position of the spacecraft.

Parameters:

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

Returns:

value of the switching function