org.orekit.frames.configuration.precessionnutation
Class PrecessionNutationCache

java.lang.Object
  org.orekit.frames.configuration.precessionnutation.PrecessionNutationCache

All Implemented Interfaces:

PrecessionNutationModel

public class PrecessionNutationCache
extends Object
implements PrecessionNutationModel

Cache for precession nutation correction computation.

This implementation includes a caching/interpolation feature to tremendously improve efficiency. The IAU-2000 model involves lots of terms (1600 components for x, 1275 components for y and 66 components for s). Recomputing all these components for each point is really slow. The shortest period for these components is about 5.5 days (one fifth of the moon revolution period), hence the pole motion is smooth at the day or week scale. This implies that these motions can be computed accurately using a few reference points per day or week and interpolated between these points. This implementation uses 12 points separated by 1/2 day (43200 seconds) each, the resulting maximal interpolation error on the frame is about 1.3×10^-10 arcseconds. -- Orekit

This class has been adapted from the CIRF2000Frame Orekit class.

Since:

1.2

Version:

$Id: PrecessionNutationCache.java 17602 2017-05-18 08:25:23Z bignon $

Author:

Rami Houdroge

Constructor Summary

PrecessionNutationCache(PrecessionNutationModel pnModel)

PrecessionNutationCache(PrecessionNutationModel pnModel, double span, int interpolationPoints)

Method Summary

double[]	getCIPMotion(AbsoluteDate date) Compute the Celestial Intermediate pole motion in the GCRS.
double[]	getCIPMotionTimeDerivative(AbsoluteDate date) Compute the Celestial Intermediate pole motion in the GCRS.
FrameConvention	getOrigin() Get IERS model origin.
boolean	isConstant() Returns true if model uses constant rotation.
boolean	isDirect() Return computation type : direct or interpolated.

Methods inherited from class java.lang.Object

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

Constructor Detail

PrecessionNutationCache

public PrecessionNutationCache(PrecessionNutationModel pnModel,
                               double span,
                               int interpolationPoints)

Parameters:

pnModel - IERS model to use

span - time spane between interpolation points

interpolationPoints - number of interpolation points to use

PrecessionNutationCache

public PrecessionNutationCache(PrecessionNutationModel pnModel)

Parameters:

pnModel - IERS model to use

Method Detail

getCIPMotion

public double[] getCIPMotion(AbsoluteDate date)

Compute the Celestial Intermediate pole motion in the GCRS.

Specified by:

getCIPMotion in interface PrecessionNutationModel

Parameters:

date - date

Returns:

CIP motion as an array of doubles

getCIPMotionTimeDerivative

public double[] getCIPMotionTimeDerivative(AbsoluteDate date)

Compute the Celestial Intermediate pole motion in the GCRS.

Specified by:

getCIPMotionTimeDerivative in interface PrecessionNutationModel

Parameters:

date - date

Returns:

CIP motion time derivatives as an array of doubles

isDirect

public boolean isDirect()

Return computation type : direct or interpolated.

Specified by:

isDirect in interface PrecessionNutationModel

Returns:

true if direct computation, false if interpolated

getOrigin

public FrameConvention getOrigin()

Get IERS model origin.

Specified by:

getOrigin in interface PrecessionNutationModel

Returns:

IERS model origin

isConstant

public boolean isConstant()

Returns true if model uses constant rotation.

Specified by:

isConstant in interface PrecessionNutationModel

Returns:

true if model uses constant rotation