A Global VLBI/LLR Analysis for the Determination of Precession and Nutation Constants

Two decades of LLR data and one decade of VLBI data are combined in a global analysis to yield improved estimates of the Earth’s precession and nutation. In this analysis, LLR provides a strong determination of precession, while VLBI is stronger in fixing nutation terms with short periods. In all, 24 nutation amplitudes are estimated. The largest correlation coefficient, between precession and 18.6 yr out-of-phase nutation in longitude, is 0.88. With the exception of some 9 yr and 18.6 yr terms, formal uncertainties are 0.1 to 0.2 milliarcseconds.