Some of the contractors had difficulties, but also the laboratory of the NFRA was not really used to producing major components (like frontend-receivers) in large numbers in a relatively short time. Integration and testing took much longer than expected, or at least much longer than was hoped for.
Test observations with a single interferometer had been carried out by the observatory staff since the spring of 1969. However, it took until February 1970 before observations could be done under computer control and with digital recording of the data on magnetic tape. An additional problem manifested itself after some time: a severe stationary CW-source of interference was clearlyvisible in all data.
Scanning the horizon with some of the array telescopes revealed that the interference originated at a military base som e tens of kilometers South-West of the observatory. A transmitter, which was part of a NATO communication network in Western Europe, was the culprit. Its frequency coincided with one of the harmonics of the WSRT's observing frequency, a band in which interfering signals were rejected to a slightly lesser extent than elsewhere in the spectrum.
Despite the fact that transmitting in this band did not violate any frequency protection rules, we found the military authorities, responsible for the network, willing to change the transmission frequency.
Administrative procedures delayed effecting the removal of the interference until the fall of 1970, though. By the end of February 1970 test observations, mostly of fairly strong point sources, were done routinely. The observations were recorded on tape and reduced in Leiden.
The earliest entries in the archive of observations are dated 23 February 1970. It took until June 1970 before observations of interesting astronomical objects were done routinely. Obviously, the interference mentioned above prevented the new telescope from producing clean maps during the first few months.
The official inauguration of the Westerbork Synthesis Radio Telescope by Her Majesty Queen Juliana of The Netherlands took place on June 24, 1970. Less than two months before that date, on the 25th anniversary of the liberation of the Netherlands from the Nazi-occupation during World War II, the Queen had dedicated a monument a mere few hundred metres away from the telescope.
The monument commemorates the many tens of thousands of people who never returned from the concentration camps to which they were transported from Camp Westerbork. It was more or less fortuitous that regular operations started just about at the time of the official inauguration, the date of which was determined more by the Queen's calendar than by the NFRA.