VLBI Standard Interface (VSI) Meeting Report

Junichi Nakajima(nakaji(AT)nict.go.jp), Yasuhiro Koyama,and Tetsuro Kondo

Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-0012, Japan

VSI-H is Just About Ready!

In the VLBI community, data transfer between the different system had been a difficult problem for a long time. Derived from diffrent VLBI media (an open reel tape, multiple VHS cassettes, and a single high density cassete), several recording systems are existing. VLBI data conversion from one to another medium often needs special interface hardware. Noriyuki Kawaguchi and his colleagues made great efforts to realize data compatibility between VLBA, S2 and K4-VSOP recorders.

Discussions of VSI (VLBI Standard Inteface) started in 1999 to achieve global compatibility among different VLBI observation systems. The issue is separated into VSI-H (hardware) and VSI-S (software). The VSI-H specification has been intensively discussed by the international VSI Technology Coordination Group (TCG) members led by Alan Whitney.

The initial VSI concept was presented by Alan Whitney in February,1999. Then he called an establishment of the VSI-TCG to VLBI communities to establish standardization in VLBI data interface. Members from CRL and National Astronomical Observatory of Japan group joined the VSI-TCG and poroposed detailed design concepts in June, 1999. Following these documents, intensive discussions were raised among international VSI-TCG members.

In 1999, Japanese group had domestic VSI meetings on 7th April, 14th May, 2nd June, 28th July, 3rd September, 5th November and 7th December. In addition to these meetings, we had three international telephone conference on 20th December 1999, 7th January 2000 and 11th May. An international meeting was also held at MIT Haystck Observatory on 8th and 9th of February, 2000. The members who attended the meeting were Alan Whitney (Haystack), Will Aldrich (Haystck), Wayne Cannon (York Univ.), George Peck (NRAO), Jon Romney (NRAO), Rick Wietfrldt (JPL), Sergei Pogrebenko (JIVE), Dick Ferris (ATNF), Noriyuki Kawaguchi (NAO), Hitoshi Kiuchi (CRL), Yasuhiro Koyama (CRL) and Junichi Nakajima (CRL). The draft for the VSI-H specifications has been revised several times and now it is under the finalaization process.

In the current soecifications, the VSI-H uses advanced LVDS (Low Voltage Differential) and attribution lines which define precise data epoch. It is expected that new instruments based on the VSI-H specifications will establish a connection with a minimum effort between diferent VLBI observation systems.

More information is available from the Web sites at the following URLs.

Finally, we would like to thank Alan Whitney and international members of the VSI Technology Coordination Group for continuous efforts to realize the VSI.

Updated on June 2, 2000. Return to CONTENTS