org.orekit.propagation.events

Class GroundAtNightDetector

java.lang.Object

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

org.orekit.propagation.events.GroundAtNightDetector

All Implemented Interfaces:

EventDetector

public class GroundAtNightDetector
extends AbstractDetector<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 and Description
static double	ASTRONOMICAL_DAWN_DUSK_ELEVATION Sun elevation at astronomical dawn/dusk (18° below horizon).
static double	CIVIL_DAWN_DUSK_ELEVATION Sun elevation at civil dawn/dusk (6° below horizon).
static 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_ITER, DEFAULT_MAXCHECK, DEFAULT_THRESHOLD

Constructor Summary

Constructors

Constructor and Description
GroundAtNightDetector(TopocentricFrame groundLocation, PVCoordinatesProvider sun, double dawnDuskElevation, AtmosphericRefractionModel refractionModel) Simple constructor.

Method Summary

Modifier and Type	Method and Description
protected GroundAtNightDetector	create(double newMaxCheck, double newThreshold, int newMaxIter, EventHandler<? super GroundAtNightDetector> newHandler) Build a new instance.
double	g(SpacecraftState state) Compute the value of the switching function.

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

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

Methods inherited from class java.lang.Object

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

Field Detail

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 Detail

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 453 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)

Method Detail

create

protected GroundAtNightDetector create(double newMaxCheck,
                                       double newThreshold,
                                       int newMaxIter,
                                       EventHandler<? super GroundAtNightDetector> newHandler)

Build a new instance.

Specified by:

create in class AbstractDetector<GroundAtNightDetector>

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

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.

Specified by:

g in interface EventDetector

Specified by:

g in class AbstractDetector<GroundAtNightDetector>

Parameters:

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

Returns:

value of the switching function