Real-time VLBI system using telephone network for online system diagnosis

Abstract

A real-time VLBI (Very Long Baseline Interferometer) system using conventional telephone lines is proposed. This system enables us to check if the VLBI network is alive by on-line manner, which is useful to reduce the loss of observation time caused by system malfunctions. In this system, a beacon of satellite or the emission from cosmic maser sources is received. The narrow-band spectral profile of the received signal leads us to compress the data up to the size less than the capacity of transmission rate on conventional telephone lines, that is to say a few tens of kbps. Additional devices for the real-time operation are A-D converters, PCs and modems, which are not special ones. As the link between the VLBI stations is performed by the conventional way, the system is applied not only to domestic VLBI networks, but also to international VLBI networks, in which a part of the VLBI stations is located in rural place. It has been confirmed that the cross-correlation is clearly detected for the compressed beacon wave data.