org.orekit.attitudes
Class CelestialBodyPointed

java.lang.Object
  org.orekit.attitudes.AbstractAttitudeLaw
      org.orekit.attitudes.CelestialBodyPointed

All Implemented Interfaces:

Serializable, AttitudeLaw, AttitudeProvider

public class CelestialBodyPointed
extends AbstractAttitudeLaw

This class handles a celestial body pointed attitude provider.

The celestial body pointed law is defined by two main elements:

• a celestial body towards which some satellite axis is exactly aimed
• a phasing reference defining the rotation around the pointing axis

The celestial body implicitly defines two of the three degrees of freedom and the phasing reference defines the remaining degree of freedom. This definition can be represented as first aligning exactly the satellite pointing axis to the current direction of the celestial body, and then to find the rotation around this axis such that the satellite phasing axis is in the half-plane defined by a cut line on the pointing axis and containing the celestial phasing reference.

In order for this definition to work, the user must ensure that the phasing reference is never aligned with the pointing reference. Since the pointed body moves as the date changes, this should be ensured regardless of the date. A simple way to do this for Sun, Moon or any planet pointing is to choose a phasing reference far from the ecliptic plane. Using Vector3D.PLUS_K, the equatorial pole, is perfect in these cases.

Instances of this class are guaranteed to be immutable.

Author:

Luc Maisonobe

See Also:

Serialized Form

Constructor Summary

CelestialBodyPointed(Frame pCelestialFrame, PVCoordinatesProvider pPointedBody, Vector3D pPhasingCel, Vector3D pPointingSat, Vector3D pPhasingSat)
Creates new instance.

Method Summary

Attitude

getAttitude(PVCoordinatesProvider pvProv, AbsoluteDate date, Frame frame) Compute the attitude corresponding to an orbital state.

Methods inherited from class org.orekit.attitudes.AbstractAttitudeLaw

getAttitude, getSpinDerivativesComputation, setSpinDerivativesComputation

Methods inherited from class java.lang.Object

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

Constructor Detail

CelestialBodyPointed

public CelestialBodyPointed(Frame pCelestialFrame,
                            PVCoordinatesProvider pPointedBody,
                            Vector3D pPhasingCel,
                            Vector3D pPointingSat,
                            Vector3D pPhasingSat)

Creates new instance.

Parameters:

pCelestialFrame - frame in which phasingCel is defined

pPointedBody - celestial body to point at

pPhasingCel - phasing reference, in celestial frame

pPointingSat - satellite vector defining the pointing direction

pPhasingSat - phasing reference, in satellite frame

Method Detail

getAttitude

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

Compute the attitude corresponding to an orbital state.

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