Very long baseline connected interferometry via the STM-16 ATM network

The Communications Research Laboratory (CRL), the National Astronomical Obs ervatory (NAO), the Institute of Space and Astronoutical Science (ISAS), an d the Telecommunication Network Laboratory Group of Nippon Telegraph and Te lephone Corporation (NTT) have developed a very-long-baseline-connected-int erferometry array, maximum baseline-length was 208 km, using a highspeed as ynchronous transfer mode (ATM) network with an AAL1 that corresponds to the constant bit-rate protocol. The very long baseline interferometry (VLBI) o bserved data is transmitted through a 2.488-Gbps [STM-16/OC-48] ATM network instead of being recorded onto magnetic tape. By combining antennas via a high-speed ATM network, a highly-sensitive virtual (radio) telescope system was realized. The system was composed of two real-time VLBI networks: the Kry-Stone-Project (KSP) network of CRL (which is used for measuring crustal deformation in the Tokyo metropolitan area), and the OLIVE (optically link ed VLBI experiment) network of NAO and ISAS which is used for astronomy (sp ace-VLBI). These networks operated in cooperation with NTT. In order to rea lize a virtual telescope, the acquired VLBI data were corrected via the ATM networks and were synthesized using the VLBI technique. The cross-correlat ion processing and data observation were done simultaneously in this system and radio flares on the weak radio source (HR1099) were detected.