Pulkovo EOP and
Reference Systems Analysis Center
Pulkovo EOP and Reference Systems Analysis Center (PERSAC) is located at the Pulkovo Observatory. Main PERSAC activities include:
Mean Pole coordinates (with prediction).
Celestial Pole Offset (CPO) and Free Core Nutation (FCN). Four daily updated CPO and FCN series (models) are provided. The CPO models are aimed primarily at users who need the maximum accuracy of the CRF<->TRF transformation without bothering about theoretical background and geophysical meaning. The CPO models can also be used for improvement of the precession and low-frequency nutation conventional model. The FCN models are aimed primarily at users who are interested in geophysical interpretation of the observations.
File fcn1.dat contains the ZM1 FCN model with variable amplitude and phase. This model is provided for the period from 1984.0 to (current date - 1.5 yr) to obtain geophysically meaningful data without significant edge effect. The IVS combined EOP series is used for computation.
File fcn3.dat contains the ZM3 FCN model with variable amplitude and phase
computes by the Sebastien Lambert's method (IERS Conventions (2010)) with three differences:
(1) ZM2 CPO series is used as input data instead of the C04 IERS CPO series,
(2) the reference interval is taken as 431 days (close to the nominal FCN period) instead of 2 years, and
(3) the FCN model coefficients are computed for every day instead of once a year.
This model is provided for the period from 1986.8 to (current date - 215 days) to obtain geophysically meaningful data without significant edge effect.
File fcn4.dat contains the ZM4 CPO model, which is the ZM3 model with addition of the bias term.
ZM2 and ZM4 models are recommended for using in all the practical tasks, which require highly accurate CRF<->TRF transformation, including real-time applications and predictions. ZM2 model is a bit less smoothed w.r.t. ZM4 model. ZM4 model provides better prediction for the prediction length 0...~200days; ZM2 model provides a bit better prediction for longer prediction length.
If you use the CPO or FCN data in your work, please cite the following paper:
Malkin Z. Empiric models of the Earth's free core nutation. Solar System Research, 2007, v. 41, No. 6, pp. 492-497.
|Contact: Zinovy Malkin, email@example.com|