Precise modeling of nutation and VLBI observations

¹ Observatoire de Paris/DANOF, URA 1125 du CNRS, 61 Avenue de l'Observatoire, 75014 Paris, France
² NASA/Goddard Space Flight Center, Geodynamics Branch, Greenbelt, Md 20771, U.S.A.

Send offprint request to: J. Souchay

Received: 16 August 1994
Accepted: 7 October 1995

Abstract

Using geodetic and astrometric VLBI acquired between 1984-1994, we have determined coefficients in the nutation series with uncertainties of 10 microarcseconds. This level of accuracy is quite sufficient to differentiate between alternate theories of nutation. We show that small terms predicted using the Kinoshita & Souchay (1990) rigid Earth theory of nutation revised by Souchay & Kinoshita (1995), agree well with the VLBI results at periods where the non rigid Earth corrections are reliable. These terms are different or absent from the Kinoshita (1977) theory that is the basis for the standard IAU 1980 model. We propose a nutation series based on the Kinoshita & Souchay theory using the Wahr (1979) transformation for a non rigid Earth that can be useful where the physical interpretation of the smaller terms is important. This series, called VKSNRE95.1, includes corrections to the nine largest terms derived from VLBI observations.