The IVS Observing Program

Starting in 2002 the IVS (International VLBI Service for Geodesy and Astrometry) is coordinating a unified geodetic and astrometric observing program to provide data for EOP and for the terrestrial and celestial reference frames. Following from the recommendations of the IVS Working Group 2 for Product Specification and Observing Programs, the unified observing program augments the previously existing weekly 24-hr EOP measurements with a second weekly, rapid-turnaround series called R1. The R1 sessions are observed with a fourfold increase in data rate using Mark IV compared to the 1993-2001 NEOS sessions, which are now designated R4. Baseline repeatability tests indicate that the R1 measurements are better than the R4 measurements. However, the R1 EOP measurements do not show a comparable improvement. The future enhancements of the IVS observing program described in the IVS WG2 report should permit detection of time variations in harmonic signals with relevance to studies of internal and external global geophysical fluids. Inclusion of other VLBI systems (e.g., the Japanese K4 and Canadian S2) with the standard Mark III/IV and introduction of new technologies such as the disk-based Mark V recorders (data rate increase up to a factor of 4 beyond the current R1 series) will increase the density of geodetic measurements and the reliability of the program.