Package org.orekit.propagation.events

Class LongitudeCrossingDetector

java.lang.Object

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

org.orekit.propagation.events.LongitudeCrossingDetector

All Implemented Interfaces:

EventDetector

public class LongitudeCrossingDetector
extends AbstractDetector<LongitudeCrossingDetector>

Detector for geographic longitude crossing.

This detector identifies when a spacecraft crosses a fixed longitude with respect to a central body.

Since:

7.1

Author:

Luc Maisonobe

Field Summary

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

DEFAULT_MAX_ITER, DEFAULT_MAXCHECK, DEFAULT_THRESHOLD

Constructor Summary

Constructors

Modifier	Constructor	Description
	LongitudeCrossingDetector(double maxCheck, double threshold, OneAxisEllipsoid body, double longitude)	Build a detector.
	LongitudeCrossingDetector(OneAxisEllipsoid body, double longitude)	Build a new detector.
protected	LongitudeCrossingDetector(AdaptableInterval maxCheck, double threshold, int maxIter, EventHandler handler, OneAxisEllipsoid body, double longitude)	Protected constructor with full parameters.

Method Summary

Modifier and Type	Method	Description
protected LongitudeCrossingDetector	create(AdaptableInterval newMaxCheck, double newThreshold, int newMaxIter, EventHandler newHandler)	Build a new instance.
double	g(SpacecraftState s)	Compute the value of the detection function.
OneAxisEllipsoid	getBody()	Get the body on which the geographic zone is defined.
double	getLongitude()	Get the fixed longitude to be crossed (radians).
void	init(SpacecraftState s0, AbsoluteDate t)	Initialize event handler at the start of a propagation.

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

getHandler, getMaxCheckInterval, getMaxIterationCount, getThreshold, 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

LongitudeCrossingDetector

public LongitudeCrossingDetector(OneAxisEllipsoid body,
                                 double longitude)

Build a new detector.

The new instance uses default values for maximal checking interval (AbstractDetector.DEFAULT_MAXCHECK) and convergence threshold (AbstractDetector.DEFAULT_THRESHOLD).

Parameters:

body - body on which the longitude is defined

longitude - longitude to be crossed

LongitudeCrossingDetector

public LongitudeCrossingDetector(double maxCheck,
                                 double threshold,
                                 OneAxisEllipsoid body,
                                 double longitude)

Build a detector.

Parameters:

maxCheck - maximal checking interval (s)

threshold - convergence threshold (s)

body - body on which the longitude is defined

longitude - longitude to be crossed

LongitudeCrossingDetector

protected LongitudeCrossingDetector(AdaptableInterval maxCheck,
                                    double threshold,
                                    int maxIter,
                                    EventHandler handler,
                                    OneAxisEllipsoid body,
                                    double longitude)

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

body - body on which the longitude is defined

longitude - longitude to be crossed

Method Detail

create

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

Build a new instance.

Specified by:

create in class AbstractDetector<LongitudeCrossingDetector>

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

getBody

public OneAxisEllipsoid getBody()

Get the body on which the geographic zone is defined.

Returns:

body on which the geographic zone is defined

getLongitude

public double getLongitude()

Get the fixed longitude to be crossed (radians).

Returns:

fixed longitude to be crossed (radians)

init

public void init(SpacecraftState s0,
                 AbsoluteDate t)

Initialize event handler at the start of a propagation.

This method is called once at the start of the propagation. It may be used by the event handler to initialize some internal data if needed.

The default implementation does nothing

This implementation sets the direction of propagation and initializes the event handler. If a subclass overrides this method it should call super.init(s0, t).

Specified by:

init in interface EventDetector

Overrides:

init in class AbstractDetector<LongitudeCrossingDetector>

Parameters:

s0 - initial state

t - target time for the integration

g

public double g(SpacecraftState s)

Compute the value of the detection function.

The value is the longitude difference between the spacecraft and the fixed longitude to be crossed, with some sign tweaks to ensure continuity. These tweaks imply the increasing flag in events detection becomes irrelevant here! As an example, the longitude of a prograde spacecraft will always increase, but this g function will increase and decrease so it will cross the zero value once per orbit, in increasing and decreasing directions on alternate orbits. If eastwards and westwards crossing have to be distinguished, the velocity direction has to be checked instead of looking at the increasing flag.

Specified by:

g in interface EventDetector

Specified by:

g in class AbstractDetector<LongitudeCrossingDetector>

Parameters:

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

Returns:

longitude difference between the spacecraft and the fixed longitude, with some sign tweaks to ensure continuity