On the Modeling of the Residual Clock Behavior in the Analysis of the Astrometric and Geodetic VLBIObservations

Based on the observations and the simulated data, the modeling of the residual clock behavior in the CALC/SOLVE system of the astrometry and geodetic VLBI data reduction was discussed. The limitations of the continuous piecewise linear modeling and the feasibility of the periodic function modeling were demonstrated. A module block of the periodic function modeling was realized in the CALC/SOLVE system. Two global solutions of 1,567 astrometric and geodetic VLBI sessions from 1990 to 2001 were performed corresponding to the two types modeling of the resicual clock behavior. It is shown that, compared with the continuous piecewise linear modeling of the residual clock behavior, the number of unknowns in the solution could be evidentry decreased and so the degree of freedom increased when the periodic function modeling was used. Though the calculated errors of the coordinates of stations and sources as well as the Earth Orientation Parameter are on the same level, it is slightly better to model the residual clock behavior by the periodic functions than the continuous piecewise linear methoe . The calculated errors of coordinates could be decreased for more than 85% of stations and 74% of sources and 51%EOP, and the mean values of the decreased formal errors are 0.02 mm , 0.3 μas and 1.5 μas respectively.