## 1. IntroductionThe dramatic improvement of the accuracy of the VLBI observations in the last decade leads to some estimations of the coefficients of the nutation of the Earth at a few microarcseconds accuracy. Thus it became necessary to be confident in the values of the coefficients of the nutation of the Earth for a simplified rigid model, at less at the microarcsecond level. In the present paper we check the analytically determined coefficients of the nutation for a rigid Earth model as calculated by Kinoshita & Souchay (1990), due to small influences of the potential of the Earth (, , , ), and to the direct torque exerted by the planets (also quoted as the direct planetary effect) up to their level of truncation, that is to say 5 microarcseconds. Moreover we calculate also the coefficients ranging between 0.1 microarcseconds and 5 microarcseconds, in order to perform a comparison with recent calculations done by Hartmann et al. (1995) and Williams (1995), respectively for the two kinds of effects above. © European Southern Observatory (ESO) 1997 Online publication: July 8, 1998 |