The Sydney University Stellar Interferometer - I. The instrument

The Sydney University Stellar Interferometer (SUSI) is a new long-baseline optical interferometer located in northern New South Wales, Australia. SUSI has been developed to tackle a range of problems in stellar astrophysics, and its design is based on a successful prototype instrument. In its initia l configuration, observations are made with a single baseline selected from an array of fixed north-south baselines covering the range from 5 to 640 m . Small apertures, wavefront-tilt correction and rapid signal sampling are employed to overcome the effects of atmospheric turbulence, and optical pat h equality is maintained by a dynamic optical delay line. The planned astro physical program mes, the resulting design criteria, the instrument and its current status are described.