org.orekit.frames

Class LocalMagneticFieldFrame

java.lang.Object

org.orekit.frames.LocalMagneticFieldFrame

All Implemented Interfaces:

LOF

public class LocalMagneticFieldFrame
extends Object
implements LOF

This class handles a magnetic field variation attitude provider.

It was designed to be used as a Bdot attitude pointing law which align a specific body axis with Earth magnetic field vector.

Attitude control thought the magnetic field is called Bdot as it follows the sinusoidal variation of the Earth magnetic field vector, along the orbit. Magnetorquers are used on board to align the instrument, as so the satellite, with the planet magnetic field, producing a sinusoidal torque along the orbit.

Author:

Alberto Ferrero, Vincent Cucchietti

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	LocalMagneticFieldFrame.LOFBuilderVector Enum defining how the +j axis of the local orbital frame will be defined.

Constructor Summary

Constructors

Constructor and Description
LocalMagneticFieldFrame(Frame inertialFrame, GeoMagneticField magneticField, Frame bodyFrame) Constructor with default definition of the local orbital frame: x: Magnetic field y: Completes orthonormal frame z: Cross product of the magnetic field with the orbital momentum .
LocalMagneticFieldFrame(Frame inertialFrame, GeoMagneticField magneticField, LocalMagneticFieldFrame.LOFBuilderVector lofBuilderVector, Frame bodyFrame) Constructor with custom definition of the local orbital frame: x: Magnetic field y: Completes orthonormal frame z: Cross product of the magnetic field with chosen vector For near-polar orbits, it is suggested to use the orbital momentum to define the local orbital frame.

Method Summary

Modifier and Type	Method and Description
Frame	getInertialFrame() Get interlai frame.
GeoMagneticField	getMagneticField() Get geomagnetid field.
String	getName() Get name of the local orbital frame.
org.hipparchus.geometry.euclidean.threed.Rotation	rotationFromInertial(AbsoluteDate date, PVCoordinates pv) Get the rotation from inertial frame to local orbital frame.
<T extends org.hipparchus.CalculusFieldElement<T>> org.hipparchus.geometry.euclidean.threed.FieldRotation<T>	rotationFromInertial(org.hipparchus.Field<T> field, FieldAbsoluteDate<T> date, FieldPVCoordinates<T> pv) Get the rotation from inertial frame to local orbital frame.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.orekit.frames.LOF

isQuasiInertial, rotationFromLOF, rotationFromLOF, rotationFromLOFInToLOFOut, rotationFromLOFInToLOFOut, transformFromInertial, transformFromInertial, transformFromLOF, transformFromLOF, transformFromLOFInToLOFOut, transformFromLOFInToLOFOut

Constructor Detail

LocalMagneticFieldFrame

public LocalMagneticFieldFrame(Frame inertialFrame,
                               GeoMagneticField magneticField,
                               Frame bodyFrame)

Constructor with default definition of the local orbital frame:

• x: Magnetic field
• y: Completes orthonormal frame
• z: Cross product of the magnetic field with the orbital momentum

. BEWARE : Do not use this constructor if it is planned to be used with an equatorial orbit as the magnetic field and orbital momentum vectors will be parallel and cause an error to be thrown

Parameters:

inertialFrame - inertial frame in which position-velocity coordinates will be given when computing transform and rotation

magneticField - Earth magnetic field model

bodyFrame - body frame related to body shape

LocalMagneticFieldFrame

public LocalMagneticFieldFrame(Frame inertialFrame,
                               GeoMagneticField magneticField,
                               LocalMagneticFieldFrame.LOFBuilderVector lofBuilderVector,
                               Frame bodyFrame)

Constructor with custom definition of the local orbital frame:

• x: Magnetic field
• y: Completes orthonormal frame
• z: Cross product of the magnetic field with chosen vector

For near-polar orbits, it is suggested to use the orbital momentum to define the local orbital frame. However, for near-equatorial orbits, it is advised to use either the position or the velocity.

Parameters:

inertialFrame - inertial frame in which position-velocity coordinates will be given when computing transform and rotation

magneticField - Earth magnetic field model

lofBuilderVector - vector used to define the local orbital frame

bodyFrame - body frame related to body shape

Method Detail

rotationFromInertial

public <T extends org.hipparchus.CalculusFieldElement<T>> org.hipparchus.geometry.euclidean.threed.FieldRotation<T> rotationFromInertial(org.hipparchus.Field<T> field,
                                                                                                                                         FieldAbsoluteDate<T> date,
                                                                                                                                         FieldPVCoordinates<T> pv)

Get the rotation from inertial frame to local orbital frame.

This rotation does not include any time derivatives. If first time derivatives (i.e. rotation rate) is needed as well, the full LOF.transformFromInertial(FieldAbsoluteDate, FieldPVCoordinates) method must be called and the complete rotation transform must be extracted from it.

Direction as X axis aligned with magnetic field vector, Y axis aligned with the cross product of the magnetic field vector with chosen vector type.

BEWARE: In this implementation, the method simply fieldify the normal rotation with given field. Hence all derivatives are lost.

Specified by:

rotationFromInertial in interface LOF

Type Parameters:

T - type of the field elements

Parameters:

field - field to which the elements belong

date - date of the rotation

pv - position-velocity of the spacecraft in some inertial frame

Returns:

rotation from inertial frame to local orbital frame

rotationFromInertial

public org.hipparchus.geometry.euclidean.threed.Rotation rotationFromInertial(AbsoluteDate date,
                                                                              PVCoordinates pv)

Get the rotation from inertial frame to local orbital frame.

This rotation does not include any time derivatives. If first time derivatives (i.e. rotation rate) is needed as well, the full transformFromInertial method must be called and the complete rotation transform must be extracted from it. Direction as X axis aligned with magnetic field vector, Z axis aligned with the cross product of the magnetic field vector with chosen vector type.

Specified by:

rotationFromInertial in interface LOF

Parameters:

date - date of the rotation

pv - position-velocity of the spacecraft in some inertial frame

Returns:

rotation from inertial frame to local orbital frame

getName

public String getName()

Get name of the local orbital frame.

Specified by:

getName in interface LOF

Returns:

name of the local orbital frame

getInertialFrame

public Frame getInertialFrame()

Get interlai frame.

Returns:

inertial frame

getMagneticField

public GeoMagneticField getMagneticField()

Get geomagnetid field.

Returns:

geo magnetic field