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Sydney University Stellar Interferometer (SUSI)

Sydney University operates an optical interferometer on the grounds of the Australia Telescope Compact Array (ATCA) observatory near Narrabri, NSW, Australia. An overview photo is presented below. For those interested in anecdotes: The four concrete pedestals in the foreground are the former foundation of one of the 96 antennas of the Culgoora Radioheliograph. Depending on the array configuration in use at the moment, one could also possibly see one of the ATCA's antennas in the background.

SUSI

Overview of SUSI, as seen from ontop one of the antennas of the ATCA (click on image for larger version)

SUSI seen from the south, with the main building on the left, the building with the delay line and the optical benches (detectors) at the centre and the tunnels and the individual siderostats on the right.

SUSI has a set of fixed north-south baselines ranging from 5 to 640 m. The incoming signal from one telescope is delayed with respect to that of another so that both can form part of one synthesised telescope's surface, which - without this correction - would not be in one plane. The SUSI delay line (or "optical pathlength correction") performing this correction by means of a mirror assembly part of which is mounted on a carriage, is shown below.

SUSI delay line with the mirror on the carriage in the foreground. The light beam enters through the hole in the back.

The photos above and below were taken near the cross point at the centre of the building near the centre of the first photo above, where the light beam enters from the telescopes and one of them is led to the delay unit, before both enter either the blue light or red light detector, depending on the experimental setup.

SUSI's optical benches, where the light beams from two telescopes are combined for registration with a detector. One can see the bench for red light (in the background) and blue light (foreground).