Package org.orekit.orbits

Class CartesianOrbit

java.lang.Object

org.orekit.orbits.Orbit

org.orekit.orbits.CartesianOrbit

All Implemented Interfaces:

TimeShiftable<ShiftablePVCoordinatesHolder<Orbit>>, TimeStamped, PVCoordinatesProvider, ShiftablePVCoordinatesHolder<Orbit>

public class CartesianOrbit
extends Orbit

This class holds Cartesian orbital parameters.

The parameters used internally are the Cartesian coordinates:

• x
• y
• z
• xDot
• yDot
• zDot

contained in PVCoordinates.

Note that the implementation of this class delegates all non-Cartesian related computations (getA(), getEquinoctialEx(), ...) to an underlying instance of the EquinoctialOrbit class. This implies that using this class only for analytical computations which are always based on non-Cartesian parameters is perfectly possible but somewhat sub-optimal.

The instance CartesianOrbit is guaranteed to be immutable.

Author:

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

See Also:

• Orbit
• KeplerianOrbit
• CircularOrbit
• EquinoctialOrbit

Field Summary

Fields inherited from class org.orekit.orbits.Orbit

TOLERANCE_POSITION_ANGLE_RATE

Constructor Summary

Constructors

Constructor	Description
CartesianOrbit(Orbit op)	Constructor from any kind of orbital parameters.
CartesianOrbit(PVCoordinates pvaCoordinates, Frame frame, AbsoluteDate date, double mu)	Constructor from Cartesian parameters.
CartesianOrbit(TimeStampedPVCoordinates pvaCoordinates, Frame frame, double mu)	Constructor from Cartesian parameters.

Method Summary

Modifier and Type	Method	Description
void	addKeplerContribution(PositionAngleType type, double gm, double[] pDot)	Add the contribution of the Keplerian motion to parameters derivatives
protected double[][]	computeJacobianEccentricWrtCartesian()	Compute the Jacobian of the orbital parameters with eccentric angle with respect to the Cartesian parameters.
protected double[][]	computeJacobianMeanWrtCartesian()	Compute the Jacobian of the orbital parameters with mean angle with respect to the Cartesian parameters.
protected double[][]	computeJacobianTrueWrtCartesian()	Compute the Jacobian of the orbital parameters with true angle with respect to the Cartesian parameters.
double	getA()	Get the semi-major axis.
double	getADot()	Get the semi-major axis derivative.
double	getE()	Get the eccentricity.
double	getEDot()	Get the eccentricity derivative.
double	getEquinoctialEx()	Get the first component of the equinoctial eccentricity vector.
double	getEquinoctialExDot()	Get the first component of the equinoctial eccentricity vector derivative.
double	getEquinoctialEy()	Get the second component of the equinoctial eccentricity vector.
double	getEquinoctialEyDot()	Get the second component of the equinoctial eccentricity vector derivative.
double	getHx()	Get the first component of the inclination vector.
double	getHxDot()	Get the first component of the inclination vector derivative.
double	getHy()	Get the second component of the inclination vector.
double	getHyDot()	Get the second component of the inclination vector derivative.
double	getI()	Get the inclination.
double	getIDot()	Get the inclination derivative.
double	getLE()	Get the eccentric longitude argument.
double	getLEDot()	Get the eccentric longitude argument derivative.
double	getLM()	Get the mean longitude argument.
double	getLMDot()	Get the mean longitude argument derivative.
double	getLv()	Get the true longitude argument.
double	getLvDot()	Get the true longitude argument derivative.
OrbitType	getType()	Get the orbit type.
boolean	hasNonKeplerianAcceleration()	Check if orbit includes non-Keplerian rates.
CartesianOrbit	inFrame(Frame inertialFrame)	Create a new object representing the same physical orbital state, but attached to a different reference frame.
protected Vector3D	initPosition()	Compute the position coordinates from the canonical parameters.
protected TimeStampedPVCoordinates	initPVCoordinates()	Compute the position/velocity coordinates from the canonical parameters.
protected Vector3D	nonKeplerianAcceleration()	Compute non-Keplerian part of the acceleration from first time derivatives.
CartesianOrbit	shiftedBy(double dt)	Get a time-shifted orbit.
CartesianOrbit	shiftedBy(TimeOffset dt)	Get a time-shifted orbit.
String	toString()	Returns a string representation of this Orbit object.

Methods inherited from class org.orekit.orbits.Orbit

fillHalfRow, fillHalfRow, fillHalfRow, fillHalfRow, fillHalfRow, fillHalfRow, getDate, getDecompositionSolver, getFrame, getJacobianWrtCartesian, getJacobianWrtParameters, getKeplerianMeanMotion, getKeplerianPeriod, getMeanAnomalyDotWrtA, getMu, getPosition, getPVCoordinates, hasNonKeplerianAcceleration, isElliptical, shiftNonKeplerian

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.orekit.utils.ShiftablePVCoordinatesHolder

getPosition, getPosition, getPVCoordinates, getPVCoordinates, getVelocity, getVelocity, getVelocity

Methods inherited from interface org.orekit.time.TimeStamped

durationFrom

Constructor Details

CartesianOrbit

public CartesianOrbit(TimeStampedPVCoordinates pvaCoordinates,
 Frame frame,
 double mu)
               throws IllegalArgumentException

Constructor from Cartesian parameters.

The acceleration provided in pvCoordinates is accessible using Orbit.getPVCoordinates() and ShiftablePVCoordinatesHolder.getPVCoordinates(Frame). All other methods use mu and the position to compute the acceleration, including shiftedBy(double) and ShiftablePVCoordinatesHolder.getPVCoordinates(AbsoluteDate, Frame).

Parameters:

pvaCoordinates - the position, velocity and acceleration of the satellite.

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

mu - central attraction coefficient (m³/s²)

Throws:

IllegalArgumentException - if frame is not a pseudo-inertial frame

CartesianOrbit

public CartesianOrbit(PVCoordinates pvaCoordinates,
 Frame frame,
 AbsoluteDate date,
 double mu)
               throws IllegalArgumentException

Constructor from Cartesian parameters.

The acceleration provided in pvCoordinates is accessible using Orbit.getPVCoordinates() and ShiftablePVCoordinatesHolder.getPVCoordinates(Frame). All other methods use mu and the position to compute the acceleration, including shiftedBy(double) and ShiftablePVCoordinatesHolder.getPVCoordinates(AbsoluteDate, Frame).

Parameters:

pvaCoordinates - the position and velocity of the satellite.

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

date - date of the orbital parameters

mu - central attraction coefficient (m³/s²)

Throws:

IllegalArgumentException - if frame is not a pseudo-inertial frame

CartesianOrbit

public CartesianOrbit(Orbit op)

Constructor from any kind of orbital parameters.

Parameters:

op - orbital parameters to copy

Method Details

getType

public OrbitType getType()

Get the orbit type.

Specified by:

getType in class Orbit

Returns:

orbit type

nonKeplerianAcceleration

protected Vector3D nonKeplerianAcceleration()

Compute non-Keplerian part of the acceleration from first time derivatives.

Overrides:

nonKeplerianAcceleration in class Orbit

Returns:

non-Keplerian part of the acceleration

getA

public double getA()

Get the semi-major axis.

Note that the semi-major axis is considered negative for hyperbolic orbits.

Specified by:

getA in class Orbit

Returns:

semi-major axis (m)

getADot

public double getADot()

Get the semi-major axis derivative.

Note that the semi-major axis is considered negative for hyperbolic orbits.

If the orbit was created without derivatives, the value returned is Double.NaN.

Specified by:

getADot in class Orbit

Returns:

semi-major axis derivative (m/s)

getE

public double getE()

Get the eccentricity.

Specified by:

getE in class Orbit

Returns:

eccentricity

getEDot

public double getEDot()

Get the eccentricity derivative.

If the orbit was created without derivatives, the value returned is Double.NaN.

Specified by:

getEDot in class Orbit

Returns:

eccentricity derivative

getI

public double getI()

Get the inclination.

Specified by:

getI in class Orbit

Returns:

inclination (rad)

getIDot

public double getIDot()

Get the inclination derivative.

If the orbit was created without derivatives, the value returned is Double.NaN.

Specified by:

getIDot in class Orbit

Returns:

inclination derivative (rad/s)

getEquinoctialEx

public double getEquinoctialEx()

Get the first component of the equinoctial eccentricity vector.

Specified by:

getEquinoctialEx in class Orbit

Returns:

first component of the equinoctial eccentricity vector

getEquinoctialExDot

public double getEquinoctialExDot()

Get the first component of the equinoctial eccentricity vector derivative.

If the orbit was created without derivatives, the value returned is Double.NaN.

Specified by:

getEquinoctialExDot in class Orbit

Returns:

first component of the equinoctial eccentricity vector derivative

getEquinoctialEy

public double getEquinoctialEy()

Get the second component of the equinoctial eccentricity vector.

Specified by:

getEquinoctialEy in class Orbit

Returns:

second component of the equinoctial eccentricity vector

getEquinoctialEyDot

public double getEquinoctialEyDot()

Get the second component of the equinoctial eccentricity vector derivative.

If the orbit was created without derivatives, the value returned is Double.NaN.

Specified by:

getEquinoctialEyDot in class Orbit

Returns:

second component of the equinoctial eccentricity vector derivative

getHx

public double getHx()

Get the first component of the inclination vector.

Specified by:

getHx in class Orbit

Returns:

first component of the inclination vector

getHxDot

public double getHxDot()

Get the first component of the inclination vector derivative.

If the orbit was created without derivatives, the value returned is Double.NaN.

Specified by:

getHxDot in class Orbit

Returns:

first component of the inclination vector derivative

getHy

public double getHy()

Get the second component of the inclination vector.

Specified by:

getHy in class Orbit

Returns:

second component of the inclination vector

getHyDot

public double getHyDot()

Get the second component of the inclination vector derivative.

If the orbit was created without derivatives, the value returned is Double.NaN.

Specified by:

getHyDot in class Orbit

Returns:

second component of the inclination vector derivative

getLv

public double getLv()

Get the true longitude argument.

Specified by:

getLv in class Orbit

Returns:

v + ω + Ω true longitude argument (rad)

getLvDot

public double getLvDot()

Get the true longitude argument derivative.

If the orbit was created without derivatives, the value returned is Double.NaN.

Specified by:

getLvDot in class Orbit

Returns:

d(v + ω + Ω)/dt true longitude argument derivative (rad/s)

getLE

public double getLE()

Get the eccentric longitude argument.

Specified by:

getLE in class Orbit

Returns:

E + ω + Ω eccentric longitude argument (rad)

getLEDot

public double getLEDot()

Get the eccentric longitude argument derivative.

If the orbit was created without derivatives, the value returned is Double.NaN.

Specified by:

getLEDot in class Orbit

Returns:

d(E + ω + Ω)/dt eccentric longitude argument derivative (rad/s)

getLM

public double getLM()

Get the mean longitude argument.

Specified by:

getLM in class Orbit

Returns:

M + ω + Ω mean longitude argument (rad)

getLMDot

public double getLMDot()

Get the mean longitude argument derivative.

If the orbit was created without derivatives, the value returned is Double.NaN.

Specified by:

getLMDot in class Orbit

Returns:

d(M + ω + Ω)/dt mean longitude argument derivative (rad/s)

hasNonKeplerianAcceleration

public boolean hasNonKeplerianAcceleration()

Check if orbit includes non-Keplerian rates.

Overrides:

hasNonKeplerianAcceleration in class Orbit

Returns:

true if orbit includes non-Keplerian derivatives

See Also:

• Orbit.getADot()
• Orbit.getEquinoctialExDot()
• Orbit.getEquinoctialEyDot()
• Orbit.getHxDot()
• Orbit.getHyDot()
• Orbit.getLEDot()
• Orbit.getLvDot()
• Orbit.getLMDot()
• Orbit.getEDot()
• Orbit.getIDot()

initPosition

protected Vector3D initPosition()

Compute the position coordinates from the canonical parameters.

Specified by:

initPosition in class Orbit

Returns:

computed position coordinates

initPVCoordinates

protected TimeStampedPVCoordinates initPVCoordinates()

Compute the position/velocity coordinates from the canonical parameters.

Specified by:

initPVCoordinates in class Orbit

Returns:

computed position/velocity coordinates

inFrame

public CartesianOrbit inFrame(Frame inertialFrame)

Create a new object representing the same physical orbital state, but attached to a different reference frame. If the new frame is not inertial, an exception will be thrown.

Specified by:

inFrame in class Orbit

Parameters:

inertialFrame - reference frame of output orbit

Returns:

orbit with different frame

shiftedBy

public CartesianOrbit shiftedBy(double dt)

Get a time-shifted orbit.

The orbit can be slightly shifted to close dates. The shifting model is a Keplerian one if no derivatives are available in the orbit, or Keplerian plus quadratic effect of the non-Keplerian acceleration if derivatives are available. Shifting is not intended as a replacement for proper orbit propagation but should be sufficient for small time shifts or coarse accuracy.

Specified by:

shiftedBy in interface TimeShiftable<ShiftablePVCoordinatesHolder<Orbit>>

Specified by:

shiftedBy in class Orbit

Parameters:

dt - time shift in seconds

Returns:

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

shiftedBy

public CartesianOrbit shiftedBy(TimeOffset dt)

Get a time-shifted orbit.

The orbit can be slightly shifted to close dates. The shifting model is a Keplerian one if no derivatives are available in the orbit, or Keplerian plus quadratic effect of the non-Keplerian acceleration if derivatives are available. Shifting is not intended as a replacement for proper orbit propagation but should be sufficient for small time shifts or coarse accuracy.

Specified by:

shiftedBy in interface TimeShiftable<ShiftablePVCoordinatesHolder<Orbit>>

Specified by:

shiftedBy in class Orbit

Parameters:

dt - time shift

Returns:

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

computeJacobianMeanWrtCartesian

protected double[][] computeJacobianMeanWrtCartesian()

Description copied from class: Orbit

Compute the Jacobian of the orbital parameters with mean angle with respect to the Cartesian parameters.

Element jacobian[i][j] is the derivative of parameter i of the orbit with respect to Cartesian coordinate j. This means each row correspond to one orbital parameter whereas columns 0 to 5 correspond to the Cartesian coordinates x, y, z, xDot, yDot and zDot.

The array returned by this method will not be modified.

Specified by:

computeJacobianMeanWrtCartesian in class Orbit

Returns:

6x6 Jacobian matrix

See Also:

• Orbit.computeJacobianEccentricWrtCartesian()
• Orbit.computeJacobianTrueWrtCartesian()

computeJacobianEccentricWrtCartesian

protected double[][] computeJacobianEccentricWrtCartesian()

Description copied from class: Orbit

Compute the Jacobian of the orbital parameters with eccentric angle with respect to the Cartesian parameters.

Element jacobian[i][j] is the derivative of parameter i of the orbit with respect to Cartesian coordinate j. This means each row correspond to one orbital parameter whereas columns 0 to 5 correspond to the Cartesian coordinates x, y, z, xDot, yDot and zDot.

The array returned by this method will not be modified.

Specified by:

computeJacobianEccentricWrtCartesian in class Orbit

Returns:

6x6 Jacobian matrix

See Also:

• Orbit.computeJacobianMeanWrtCartesian()
• Orbit.computeJacobianTrueWrtCartesian()

computeJacobianTrueWrtCartesian

protected double[][] computeJacobianTrueWrtCartesian()

Description copied from class: Orbit

Compute the Jacobian of the orbital parameters with true angle with respect to the Cartesian parameters.

Element jacobian[i][j] is the derivative of parameter i of the orbit with respect to Cartesian coordinate j. This means each row correspond to one orbital parameter whereas columns 0 to 5 correspond to the Cartesian coordinates x, y, z, xDot, yDot and zDot.

The array returned by this method will not be modified.

Specified by:

computeJacobianTrueWrtCartesian in class Orbit

Returns:

6x6 Jacobian matrix

See Also:

• Orbit.computeJacobianMeanWrtCartesian()
• Orbit.computeJacobianEccentricWrtCartesian()

addKeplerContribution

public void addKeplerContribution(PositionAngleType type,
 double gm,
 double[] pDot)

Add the contribution of the Keplerian motion to parameters derivatives

This method is used by integration-based propagators to evaluate the part of Keplerian motion to evolution of the orbital state.

Specified by:

addKeplerContribution in class Orbit

Parameters:

type - type of the position angle in the state

gm - attraction coefficient to use

pDot - array containing orbital state derivatives to update (the Keplerian part must be added to the array components, as the array may already contain some non-zero elements corresponding to non-Keplerian parts)

toString

public String toString()

Returns a string representation of this Orbit object.

Overrides:

toString in class Object

Returns:

a string representation of this object