EVALUATION OF REPEATABILITY OF BASE-LINE LENGTHS IN THE VLBI NETWORK AROUND THE TOKYO METROPOLITAN-AREA

Since 1995, VLBI measurements using fixed VLBI stations around the Tok yo metropolitan area have been continually producing data of station p ositions and baseline lengths. The accuracy of baseline length measure ments is evaluated in terms of repeatability, conventionally defined a s a standard deviation of those obtained by five continuous sessions. Continuous improvement both in system hardware and in the observation method have resulted in a remarkable improvement in measurement accura cy. Repeatability reaches about a 2-mm level in baseline length in our VLBI network.