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Long-Term Nutation and the Length Day Variation from VLBI Observations

E. I. Yagudina, I. S. Sudnik

Proceedings of the International Astronomical Union, In: J.A. Hughes, C.A. Smith & G.H. Kaplan (Eds.) IAU Colloquim 127: Reference Systems, University of Waikato, 381-384 (1991)

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The shift of the celestial pole with respect to its 1980 position in longitude (Δψ) and obliquity (Δε) from the available VLBI measurement of 1984 year within IRIS project is estimated. Formal uncertainties of the angles Δψ and Δε are 5.9 mas and 2.7 mas respectively. The day length variation was obtained from the same data. Then attempt was made to obtain annual and semiannual nutation amplitudes. The values are in reasonable agreement with the determinations of other workers.