Self-phase-referencing interferometry with SUSI

The Sydney University Stellar Interferometer (SUSI) is being fitted with a new beam combiner, called the Micro-arcsecond University of Sydney Companion Astrometry instrument (MUSCA), for the purpose of high precision astrometry of bright binary stars. Operating in the visible wavelength regime where photon-counting and post-processing fringe tracking is possible, MUSCA will be used in tandem with SUSI's primary beam combiner, Precision Astronomical Visible Observations (PAVO), to record high spatial resolution fringes and thereby measure the separation of fringe packets of binary stars. With continued monitoring of stellar separation vectors at precisions in the tens of micro-arcseconds over timescales of years, it will be possible to search for the presence of gravitational perturbations in the orbital motion such as those expected from planetary mass objects in the system. This paper describes the first phase of the development, which includes the setup of the dual beam combiner system and the methodology applied to stabilize fringes of a star by means of self-phase-referencing.