A hierarchical phasing algorithm for multi–element optical interferometers

¹ Collège de France & University of Manchester, Nuffield Radio Astronomy Laboratories, Jodrell Bank, UK–Cheshire, SK11 9DL, UK
² Collège de France et Observatoire de Haute–Provence, CNRS, F–04870 Saint–Michel l'Observatoire, France

Received: 26 February 1999
Accepted: 26 March 1999

Abstract

Large multi–aperture interferometers are expected to provide snap–shot images with milli– to nano–arcsecond resolution, directly at the combined focus. This requires a densified exit pupil and phased beams for all the wavelengths used. The wave analysis methods serving for adaptive optics in monolithic telescopes being inadequate for diluted apertures, we have developed a different phasing algorithm. It involves a hierarchy of aperture triplets and uses image sharpness criteria. Numerical simulations on unresolved and resolved objects show that a single iteration is generally sufficient. On wavelength–dependant objects, the proper position indexing of the monochromatic image components appears also efficiently achievable.