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VLBI: when people care about picoseconds, but can't remember the date

Submitter: Ilse van Bemmel
Description: According to the plaque in the image above, today marks the 50th anniversary of the first successful VLBI (Very Long Baseline Interferometry) experiment. This was conducted in Canada on 17th April 1967, where the 26-m dish at Dominion Radio Astrophysical Observatory (which bears the plaque) and a dish at Algonquin Radio Observatory were coordinated to observe a single bright, but compact radio source.

Tracing back the events makes it clear that the Canadian effort was the lucky one of many similar VLBI experiments taking place near simultaneously. There was a friendly rivalry between at least five teams, four in the US and one in Canada, and the cross-fertilization from this was essential to achieve success.

The year 1967 was densely packed with VLBI successes. In a paper reflecting on 30 years of VLBI, Jim Moran, from the US, lists several experiments in that year alone, though none on 17th April. Interestingly there are now slight inconsistencies in the recollections of the events. What is apparent is that at some point in the Spring fringes were detected - Norman Broten, from the Canadian team, recalls this happening on the 20th May, from observations recorded on 15th or 16th April, with a frantic effort to then present the work at URSI in Ottawa on 22nd May. By the time the Canadian experiments were published in Nature and Science, the US teams had reported several successful experiments as well.

It is no longer clear why 17th April 1967 was chosen to commemorate the first successful experiment in Canada. It is clear however, that this was a global effort that incorporated technical and theoretical contributions from many countries. In recognition of the hard work from the VLBI pioneers 50 years ago, we pay homage to all the teams who opened up the VLBI window on the Universe.
Copyright: JIVE
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