org.orekit.attitudes

Class LofOffset

java.lang.Object

org.orekit.attitudes.LofOffset

All Implemented Interfaces:

Serializable, 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

See Also:

Serialized Form

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

Methods

Modifier and Type	Method and Description
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)
          throws OrekitException

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

Throws:

OrekitException - if inertialFrame is not a pseudo-inertial frame

LofOffset

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

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. The underlying definitions used in commons-math Rotation(RotationOrder, double, double, double) use reversed definition, i.e. they correspond to a vectors field rotating with respect to a fixed frame. So to retrieve the angles provided here from the commons-math underlying rotation, one has to revert the rotation, 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.applyTo(alignedAtt.revert());

   // note the call to revert in the following statement
   double[] angles = offsetProper.revert().getAngles(order);

   System.out.println(alpha1 + " == " + angles[0]);
   System.out.println(alpha2 + " == " + angles[1]);
   System.out.println(alpha3 + " == " + angles[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

Throws:

OrekitException - if inertialFrame is not a pseudo-inertial frame

Method Detail

getAttitude

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

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

Throws:

OrekitException - if attitude cannot be computed