ESTIMATION OF VISIBILITY AMPLITUDE BY OPTICAL LONG-BASE-LINE MICHELSON INTERFEROMETRY WITH LARGE APERTURES

A long-baseline Michelson interferometer samples the Fourier transform of the brightness distribution of a source through measurements of fr inge visibilities. The most fundamental problem in processing interfer ometric data is the derivation of a visibility estimate which is indep endent of the effects of atmospheric turbulence. This is an important problem for optical observations, most notably for large apertures in a multi-speckle mode, as is the case with the Grand Interferometre a 2 Telescopes (GI2T). Here we describe a new estimator of the visibility amplitude, which is insensitive to the seeing conditions and the expo sure time. The theory is presented along with numerical simulations, a nd the new estimator is used to analyse data collected with the GI2T o n alpha Lyrae and tau Cygni.