The increased accuracy of VLBI measurements over the past few years has lead to the extension of many of the models of the motion of the Earth in inertial space. In particular, there have now been a number of studies reporting on the detection of tidally coherent Earth rotation rate and pole position variations in the diurnal and semidiurnal bands [ Herring, 1993; Sovers et al., 1993; Freedman et al., 1994; Herring and Dong, 1994]. The magnitudes of these signals can reach 80 microseconds for Universal Time (UT1) and 600 micro-arc-seconds for pole positions corresponding to surface displacements of 20--30 mm at the Earth's surface. In this regard, accounting for these variations is important for achieving the highest accuracy geodetic parameter estimates. To further understand, the high frequency variations in Earth rotation, two intense VLBI campaigns that featured continuous VLBI experiments for two weeks have been organized in July 1992 (Epoch-92) and January 1994 (Cont-94). Results from the Epoch-92 campaign have been published in a number of different locations and the results from the campaign summarized in Dickey and Feissel [1994]. Only preliminary analyses of the Cont-94 campaign results have been carried out so far but the campaign appears to have generated a very high quality data set.
Acknowledgments. This work was supported by the National Aeronautics and Space Administration under grant NAG 5-538 and NAW-0037, by the National Oceanic and Atmospheric Administration under grant NA90AA-D-AC481, and by the Kerr-McGee Foundation. The views expressed herein are those of the author and do not necessarily reflect the views of NOAA or any of its subagencies.