We have developed a new VLBI system based on the conventional K-4 system, whose data-acquisition mode includes VLBA and VSOP data modes. In developing the new VLBI data-acquisition system, multi-bit quantization sampling, high-speed (wide-bandwidth) data sampling, and the data acquisition mode were taken into consideration. The new acquisition system has one-bit and two-bit quantization sampling modes for VLBI, and four-bit and eight-bit sampling modes for general-purpose use. The total data rate is up to 256 Mbps, and up to 16 video channels can be selected. Anti-aliasing filtering is carried out in analog (32 MHz), and after sampling, the 16-MHz, 8-MHz, etc. filterings are carried out in the digital filter. The digital filter is used because it results in good phase characteristics. This system is specially designed for the Key Stone Project, and an input interface unit is incorporated in the VSOP.
We conducted VLBI experiments on the pulsar PSR 0329+54 with the Kashima (Japan)-Kalyazin (Russia) baseline in 1995 March and 1996 May. An absolute astrometric measurement was applied by using the analysis software SOLVE and CALC, which were developed by NASA/GSFC for geodesy and astrometry. Our measurement results are consistent with the former results of a VLBI observation by Bartel et al. (1985, AAA 39.041.005) and a VLA observation by Fomalont et al. (1984, AAA 38.041.014) when proper motion (Harrison et al. 1993, AAA 57.126.049) is taken into account. By using our data set and Bartel et al.'s data, the most precise proper motion and pulsar position in ICRF were obtained. The proper motion as μα : 17.3 ± 0.8 mas yr−1, μδ : –11.5 ± 0.6 mas yr−1 and the coordinates at the epoch of 1995.0 are α : 03h32m59.s376 ± 0.001, and δ : 54°34′43.″504 ± 0.007.
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