The geodetic VLBI community has recently formed the International VLBI Service (IVS) organization to organize, coordinate and standardize geodetic VLBI practices. IVS counts some 80 organizations from 14 countries among its charter members, quite a few of them also involved with astronomical VLBI. Among the members of the IVS board of directors are a Technical Coordinator (Alan Whitney, MIT Haystack Observatory) and Technical Representatives (Wayne Cannon, York University, Canada and Tetsuro Kondo, CRL, Japan). Among the directives to this group is to 'strive to ensure the highest degree of global compatibility of VLBI data-acquisition systems'.
Within the astronomy VLBI community, the Global VLBI Working Group (GVWG), originally formed to assist the organization and execution of the space-VLBI programs of VSOP and RadioAstron, is still in place, with Richard Schilizzi of JIVE as the chairman. Some time ago Richard appointed Alan Whitney and Wayne Cannon as co-chairman of the GVWG Technology Coordination Group and charged them with, among other things, to pursue the holy grail of VLBI compatibility. We have been a bit slow to answer the charge, but action is now picking up.
As part of the process to move towards the compatibility goal, we feel that it is necessary to involve a group of technical experts, namely yourselves, who have had wide experience with the existing set of VLBI data-acquisition and correlator systems, and who collectively can exercise their wisdom to define a 'standard VLBI interface' towards which the VLBI community can strive. This idealistic future will not happen overnite, but the goal is to start on a path that will show the way, and then to encourage the worldwide community to follow it as systems are updated or created.
1. Place a draft standard on the table (one exists, which you may or may not have yet seen).
2. Interact via e-mail communications to exchange comments, suggestions and constructive criticisms. [An e-mail exploder will be set up for easy communications within the group.]
3. Pursue a gentleman's agreement on a standard. At some point it may be necessary for some or all of the members of the committee to meet face-to-face to hammer out agreements on sticking points.
4. Formalize the standard in a technical memorandum to be distributed to the community.
5. Update the standard as necessary.
6. Guide and encourage implementation of the standard whenever possible.
If you feel this process can be improved upon, we are happy to hear your suggestions.
The Proposed Members of the Committee
The proposed members of the committee, covering both astronomical and geodetic interests, are:
Alan Whitney, MIT Haystack Observatory, USA (IVS Tech Coord, GVWG Tech
Coord Group co-chair)
Wayne Cannon, York University, Canada (IVS Tech Representative, GVWG Tech
Coord Group co-chair)
Tetsuro Kondo, CRL, Japan (IVS Tech Representative)
Brent Carlson, DRAO, Canada
Dick Ferris, ATNF, Australia
Dave Graham, MPI, Germany
Nori Kawaguchi, NAO, Japan
Sergei Pogrebenko, JIVE, The Netherlands
Jon Romney, NRAO, USA
Ralph Spencer, Jodrell Bank, England
If the development of a VSI specification is successful, it may be desirable to try to extend standardization even further, defining standard 'sampler modules' and/or 'BBC modules' which may be of value to the VLBI community.
1. A proposal drafted by Alan Whitney following discussions arising from a meeting in Jan 99 in Japan involving Canadian, Japanese and American representatives. This document outlines primarily the high-level description of the proposed interfaces and lacks detailed electrical and timing information, which the Tetsuro Kondo and his associates at CRL graciously offered to fill in. This document, along with comments already received, can be viewed at http://dopey.haystack.mit.edu/vsi.
2. An electrical and timing draft proposal arising from work within CRL and with discussions in the broader Japanese community. This document can be viewed at //www2.nict.go.jp/aeri/sts/stmg/ivstdc/ivs/vsi
If you are willing to participate in this effort, please respond to Alan
Whitney at
We look forward to hearing from you in the near future.
Regards,
Alan Whitney
Wayne Cannon
Tetsuro Kondo