On the Accuracy of the 1980 IAU Nutation Series

Abstract

At the Seventeenth IAU General Assembly in Montreal, Canada, in 1979, the resolution was passed adopting the 1979 Nutation Series, which was based on : — the development of the rigid theory by Kinoshita (1977); — the modifications to this theory allowing for the effects of a fluid core and an elastic shell (Molodensky, 1961). The purpose of this action has been nothing but the adoption of a working Standard on Nutation. The details that follow are well known (Seidelmann, 1980). After a discussion at IAU Colloquium N°56 in Warsaw, Poland, in 1980, the Working Group on Nutation decided to recommend a change to the 1980 IAU Nutation Series, which is based on the theory developed by Wahr (1980). The differences between the above mentioned Series are within the limits of ±0.002 and are not detectable with the present observational accuracy. As an example, we summarized in Table 1 the observed amplitudes of circular nutation component $2{{L}_{\mathbb{C}}} - \alpha$ which were determined from astronomical observations with best accuracy. The effect of 0₁-tide on this component is taken into account by using the theoretical tide with Λ=l+ k–l=1.2. The theoretical amplitudes of this component were reduced to the mean epochs of observations.