org.orekit.orbits
Class Orbit

java.lang.Object
  org.orekit.orbits.Orbit

All Implemented Interfaces:

java.io.Serializable, TimeStamped

Direct Known Subclasses:

CartesianOrbit, CircularOrbit, EquinoctialOrbit, KeplerianOrbit

public abstract class Orbit
extends java.lang.Object
implements TimeStamped, java.io.Serializable

This class handles orbital parameters without date.

The aim of this class is to separate the orbital parameters from the date for cases where dates are managed elsewhere. This occurs for example during numerical integration and interpolation because date is the free parameter whereas the orbital parameters are bound to either differential or interpolation equations.

For user convenience, both the cartesian and the equinoctial elements are provided by this class, regardless of the canonical representation implemented in the derived class (which may be classical keplerian elements for example).

The parameters are defined in a frame specified by the user. It is important to make sure this frame is consistent: it probably is inertial and centered on the central body. This information is used for example by some force models.

The object OrbitalParameters is guaranteed to be immutable.

Version:

$Revision:1665 $ $Date:2008-06-11 12:12:59 +0200 (mer., 11 juin 2008) $

Author:

Luc Maisonobe, Guylaine Prat, Fabien Maussion, Véronique Pommier-Maurussane

See Also:

Serialized Form

Constructor Summary

protected	Orbit(Frame frame, AbsoluteDate date, double mu) Default constructor.
protected	Orbit(PVCoordinates pvCoordinates, Frame frame, AbsoluteDate date, double mu) Set the orbit from cartesian parameters.

Method Summary

abstract double	getA() Get the semi-major axis.
AbsoluteDate	getDate() Get the date of orbital parameters.
abstract double	getE() Get the eccentricity.
abstract double	getEquinoctialEx() Get the first component of the equinoctial eccentricity vector.
abstract double	getEquinoctialEy() Get the second component of the equinoctial eccentricity vector.
Frame	getFrame() Get the frame in which the orbital parameters are defined.
abstract double	getHx() Get the first component of the inclination vector.
abstract double	getHy() Get the second component of the inclination vector.
abstract double	getI() Get the inclination.
double	getKeplerianMeanMotion() Get the keplerian mean motion.
double	getKeplerianPeriod() Get the keplerian period.
abstract double	getLE() Get the eccentric latitude argument.
abstract double	getLM() Get the mean latitude argument.
abstract double	getLv() Get the true latitude argument.
double	getMu() Get the central acceleration constant.
PVCoordinates	getPVCoordinates() Get the PVCoordinates in definition frame.
PVCoordinates	getPVCoordinates(Frame outputFrame) Get the PVCoordinates.
abstract Orbit	shiftedBy(double dt) Get a time-shifted orbit.

Methods inherited from class java.lang.Object

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

Constructor Detail

Orbit

protected Orbit(Frame frame,
                AbsoluteDate date,
                double mu)
         throws java.lang.IllegalArgumentException

Default constructor. Build a new instance with arbitrary default elements.

Parameters:

frame - the frame in which the parameters are defined (must be a quasi-inertial frame)

date - date of the orbital parameters

mu - central attraction coefficient (m^3/s^2)

Throws:

java.lang.IllegalArgumentException - if frame is not a quasi-inertial frame

Orbit

protected Orbit(PVCoordinates pvCoordinates,
                Frame frame,
                AbsoluteDate date,
                double mu)
         throws java.lang.IllegalArgumentException

Set the orbit from cartesian parameters.

Parameters:

pvCoordinates - the position and velocity in the inertial frame

frame - the frame in which the PVCoordinates are defined (must be a quasi-inertial frame)

date - date of the orbital parameters

mu - central attraction coefficient (m^3/s^2)

Throws:

java.lang.IllegalArgumentException - if frame is not a quasi-inertial frame

Method Detail

getFrame

public Frame getFrame()

Get the frame in which the orbital parameters are defined.

Returns:

frame in which the orbital parameters are defined

getA

public abstract double getA()

Get the semi-major axis.

Returns:

semi-major axis (m)

getEquinoctialEx

public abstract double getEquinoctialEx()

Get the first component of the equinoctial eccentricity vector.

Returns:

first component of the equinoctial eccentricity vector

getEquinoctialEy

public abstract double getEquinoctialEy()

Get the second component of the equinoctial eccentricity vector.

Returns:

second component of the equinoctial eccentricity vector

getHx

public abstract double getHx()

Get the first component of the inclination vector.

Returns:

first component of the inclination vector

getHy

public abstract double getHy()

Get the second component of the inclination vector.

Returns:

second component of the inclination vector

getLE

public abstract double getLE()

Get the eccentric latitude argument.

Returns:

eccentric latitude argument (rad)

getLv

public abstract double getLv()

Get the true latitude argument.

Returns:

true latitude argument (rad)

getLM

public abstract double getLM()

Get the mean latitude argument.

Returns:

mean latitude argument (rad)

getE

public abstract double getE()

Get the eccentricity.

Returns:

eccentricity

getI

public abstract double getI()

Get the inclination.

Returns:

inclination (rad)

getMu

public double getMu()

Get the central acceleration constant.

Returns:

central acceleration constant

getKeplerianPeriod

public double getKeplerianPeriod()

Get the keplerian period.

The keplerian period is computed directly from semi major axis and central acceleration constant.

Returns:

keplerian period in seconds

getKeplerianMeanMotion

public double getKeplerianMeanMotion()

Get the keplerian mean motion.

The keplerian mean motion is computed directly from semi major axis and central acceleration constant.

Returns:

keplerian mean motion in radians per second

getDate

public AbsoluteDate getDate()

Get the date of orbital parameters.

Specified by:

getDate in interface TimeStamped

Returns:

date of the orbital parameters

getPVCoordinates

public PVCoordinates getPVCoordinates(Frame outputFrame)
                               throws OrekitException

Get the PVCoordinates.

Parameters:

outputFrame - frame in which the position/velocity coordinates shall be computed

Returns:

pvCoordinates in the specified output frame

Throws:

OrekitException - if transformation between frames cannot be computed

See Also:

getPVCoordinates()

getPVCoordinates

public PVCoordinates getPVCoordinates()

Get the PVCoordinates in definition frame.

Returns:

pvCoordinates in the definition frame

See Also:

getPVCoordinates(Frame)

shiftedBy

public abstract Orbit shiftedBy(double dt)

Get a time-shifted orbit.

The orbit can be slightly shifted to close dates. This shift is based on a simple keplerian model. It is not intended as a replacement for proper orbit and attitude propagation but should be sufficient for small time shifts or coarse accuracy.

Parameters:

dt - time shift in seconds

Returns:

a new orbit, shifted with respect to the instance (which is immutable)

See Also:

AbsoluteDate.shiftedBy(double), PVCoordinates.shiftedBy(double), Attitude.shiftedBy(double), SpacecraftState.shiftedBy(double)