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Very Long Baseline Interferometry (VLBI) is conducted by combining signals
from widely separated telescopes, each of which has its own time and
frequency standard. (For this reason, some of the first VLBI observations
were described as Independent Local Oscillator Interferometry.)
Ken Kellermann
in the chapter on VLBI of his book "Open Skies"
describes how several groups worked towards the first VLBI observations
in the mid 1960s, with the first successful VLBI observations
being made in April 1967 in Canada and May 1967 in the USA, with
these preceded by several unsuccessful attempts.
The first Australian efforts were very close behind, with successful
observations made in June 1967 using antennas of NASA's Deep
Space Network at Island Lagoon, near Woomera in South Australia (pictured above), and
Tidbinbilla.
The 26m (85-foot) diameter DSS-41 at Island Lagoon, was opened in 1961 and closed in December 1972,
playing a role in tracking early Mariner, Pioneer, and Lunar Orbiter missions over its lifetime.
It participated in a number of VLBI observations by a team led by Jack Gubbay,
including baselines to Goldstone (USA) and Johannesburg (South Africa) antennas of NASA's Deep Space Network,
and with its last VLBI observations being made in November 1972
(Image credit: Don Gray, Colin Mackellar, and honeysucklecreek.net)
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