Communications Research Laboratory (CRL) is developing a real-time VLBI technique for geodetic use in cooperation with Telecommunication Network Laboratory Group of Nippon Telegraph and Telephone Corpolation (NTT). The real-time VLBI means that correlation processing is made in real time like a connected element interferometer. In May,1996 the first fringes were successfully detected on Kashima-Koganei baseline (about 100 km) (Fig.1). In real-time VLBI digitized data of radio signals from quasers are directly transmitted to a central station where a correlator is located using ATM (Asyncronous Transfer Mode with a speed of 256 Mbps) networks consisting of optical fiber link instead of recording on a magnetic tape. (T.K.)
Figure 1. First real-time VLBI fringes after bandwidth synthesis of 8 channels in 8 GHz band for 4C39.25 on the Kashima-Koganei baseline.