org.orekit.attitudes

Class LofOffset

java.lang.Object

org.orekit.attitudes.LofOffset

All Implemented Interfaces:

AttitudeProvider

public class LofOffset
extends Object
implements AttitudeProvider

Attitude law defined by fixed Roll, Pitch and Yaw angles (in any order) with respect to a local orbital frame.

The attitude provider is defined as a rotation offset from some local orbital frame.

Author:

Véronique Pommier-Maurussane

Constructor Summary

Constructors

Constructor and Description
LofOffset(Frame inertialFrame, LOFType type) Create a LOF-aligned attitude.
LofOffset(Frame inertialFrame, LOFType type, RotationOrder order, double alpha1, double alpha2, double alpha3) Creates new instance.

Method Summary

Modifier and Type	Method and Description
<T extends RealFieldElement<T>> FieldAttitude<T>	getAttitude(FieldPVCoordinatesProvider<T> pvProv, FieldAbsoluteDate<T> date, Frame frame) Compute the attitude corresponding to an orbital state.
Attitude	getAttitude(PVCoordinatesProvider pvProv, AbsoluteDate date, Frame frame) Compute the attitude corresponding to an orbital state.

Methods inherited from class java.lang.Object

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

Constructor Detail

LofOffset

public LofOffset(Frame inertialFrame,
                 LOFType type)

Create a LOF-aligned attitude.

Calling this constructor is equivalent to call LofOffset(inertialFrame, LOFType, RotationOrder.XYZ, 0, 0, 0)

Parameters:

inertialFrame - inertial frame with respect to which orbit should be computed

type - type of Local Orbital Frame

LofOffset

public LofOffset(Frame inertialFrame,
                 LOFType type,
                 RotationOrder order,
                 double alpha1,
                 double alpha2,
                 double alpha3)

Creates new instance.

An important thing to note is that the rotation order and angles signs used here are compliant with an attitude definition, i.e. they correspond to a frame that rotate in a field of fixed vectors. So to retrieve the angles provided here from the Hipparchus underlying rotation, one has to either use the RotationConvention.VECTOR_OPERATOR and revert the rotation, or to use RotationConvention.FRAME_TRANSFORM as in the following code snippet:

   LofOffset law          = new LofOffset(inertial, lofType, order, alpha1, alpha2, alpha3);
   Rotation  offsetAtt    = law.getAttitude(orbit).getRotation();
   Rotation  alignedAtt   = new LofOffset(inertial, lofType).getAttitude(orbit).getRotation();
   Rotation  offsetProper = offsetAtt.compose(alignedAtt.revert(), RotationConvention.VECTOR_OPERATOR);

   // note the call to revert and the conventions in the following statement
   double[] anglesV = offsetProper.revert().getAngles(order, RotationConvention.VECTOR_OPERATOR);
   System.out.println(alpha1 + " == " + anglesV[0]);
   System.out.println(alpha2 + " == " + anglesV[1]);
   System.out.println(alpha3 + " == " + anglesV[2]);

   // note the conventions in the following statement
   double[] anglesF = offsetProper.getAngles(order, RotationConvention.FRAME_TRANSFORM);
   System.out.println(alpha1 + " == " + anglesF[0]);
   System.out.println(alpha2 + " == " + anglesF[1]);
   System.out.println(alpha3 + " == " + anglesF[2]);
 

Parameters:

inertialFrame - inertial frame with respect to which orbit should be computed

type - type of Local Orbital Frame

order - order of rotations to use for (alpha1, alpha2, alpha3) composition

alpha1 - angle of the first elementary rotation

alpha2 - angle of the second elementary rotation

alpha3 - angle of the third elementary rotation

Method Detail

getAttitude

public Attitude getAttitude(PVCoordinatesProvider pvProv,
                            AbsoluteDate date,
                            Frame frame)

Compute the attitude corresponding to an orbital state.

Specified by:

getAttitude in interface AttitudeProvider

Parameters:

pvProv - local position-velocity provider around current date

date - current date

frame - reference frame from which attitude is computed

Returns:

attitude attitude on the specified date and position-velocity state

getAttitude

public <T extends RealFieldElement<T>> FieldAttitude<T> getAttitude(FieldPVCoordinatesProvider<T> pvProv,
                                                                    FieldAbsoluteDate<T> date,
                                                                    Frame frame)

Compute the attitude corresponding to an orbital state.

Specified by:

getAttitude in interface AttitudeProvider

Type Parameters:

T - type of the field elements

Parameters:

pvProv - local position-velocity provider around current date

date - current date

frame - reference frame from which attitude is computed

Returns:

attitude attitude on the specified date and position-velocity state