Accuracy of proposed corrections to the current precession-nutation models: A first assessment

Since 2020 a few research groups have reported new estimations of nutation amplitudes or precession parameters, usually presented as corrections to the nutation and precession theories IAU2000 and IAU2006, as well as new empirical models for the free core nutation (FCN). The main effect of those proposed corrections is reducing the unexplained variance of the celestial pole offsets (CPO) time series. The improvement of the accuracy of CPO models was encouraged by Resolution 5 of the 2019 General Assembly of the International Association of Geodesy (IAG), included among the recommendations of the GGOS/IERS Unified Analysis Workshop held that year, and also supported by Resolution B2 of the International Astronomical Union (IAU) in 2021.

The variance reduction attainable by refining the precession offsets and rates and the amplitudes of the forced nutations is noticeably larger than that resulting from the corrections needed for the consistency of the precession and nutation theories (Escapa et al 2018). However, the amount of the improvement depends strongly on the various fitting strategies, the input CPO series and the time periods chosen for benchmarking.

That fact is shown through the accuracy assessment of a selection of correction models proposed by the authors and other teams, either supplemented with FCN models or not, and for a selection of input CPO data and time spans.

 

The work of JMF, AE, and TB was partially supported by Spanish Projects PID2020-119383GB-I00 funded by MCIN/AEI/10.13039/501100011033 and PROMETEO/2021/030 (Generalitat Valenciana); and SB was  supported partially by Generalitat Valenciana (SEJIGENT/2021/001) and the European Union˜NextGenerationEU (ZAMBRANO 21-04) .