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12th of August 2022
20th Anniversary of first ATCA North-Spur Fringes
When it was first constructed in the late 1980s, the Australia Telescope Compact Array had a 3-km East-West rail track for five antennas to be moved along ( and a ~50m section of track 3km further west that antenna CA06 could be moved on). In 1996, Major National Research Funding (MNRF) was received to upgrade the capabilities of the array from its existing 1, 2, 4, and 8 GHz receivers to include 15mm and 3mm bands. In the cm bands, observations of a (southern) source could be made over 12 hours, taking advantage of the Earth's rotation to cover a full range of baseline orientations, with respect to the celestial source, to make good images. However, the atmosphere becomes more opaque at low elevations in the mm-bands, and so it is advantageous to have a two-dimensional array so that imaging can be made on shorter timescales. A 214m North-South spur was added to the array in the late 1990s, enabling two of the inner 5 antennas to be placed on that track in compact "hybrid" arrays. The image above marks the occasion -- twenty years ago today -- when the first successful observations were made with antennas on the North-South spur, of the ATCA primary flux density calibrator PKS 1934-638. The plot of the interferometric fringes was signed by those in attendance and who had contributed to this achievement. The framed plot is displayed in the Control Building at the Compact Array.

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