Expected accuracy of the 1900-1990 earth orientation parameters in the HIPPARCOS reference frame

Abstract

Based on the space and time distribution of observations available over 1900-1990 for estimating the motion of the earth rotation axis in space and relative to the earth's crust, and universal time, we evaluate the accuracy of the earth orientation parameters in the framework of their global analysis in the Hipparcos reference frame currently under preparation. Considering three test 20-yr periods (1900-1920, 1935-1955, 1965-1985) and 5-day solution, we conclude that polar motion can be known to +/- 0.030 arcsec in the first part of the century and +/- 0.009 arcsec in the last part, and universal time to +/- 0.0008 arcsec from the advent of atomic time. As for the position of the earth's rotation axis in space, its expected uncertainty is of the order of +/- 0.02-0.08 arcsec at the beginning of the century and +/-0.01 arcsec in the last period studied. The expected time evolution of the correlations and error ellipses is also studied. The results over 90 yr of this homogeneous and high resolution analysis will bring new insight on precession and nutations as well as on climatic changes over the century.