New approaches to the design of non-redundant aperture masks

The spatial frequencies accessible with a non-redundant mask (NRM) are fixed by the relative positions of the sub-apertures over the telescope pupil. In this paper we present several iterative algorithms for constructing nonredundant sub-apertures configurations. We use the triple correlation of a pre-existing set of n sub-apertures in order to find if, and where, a supplementary n+1th sub-aperture can be placed. As several possible locations may be found, we propose 3 different criteria to choose among them. Favoring the positions that are the closest to the center of mass of the sub-apertures ends up finding configurations similar to those described by Golay. The 2 other criteria aim at favoring higher spatial frequencies. The possibility of working with pupils of different radii in order to obtain a better coverage is briefly explored. The comparison between the configurations found with the 3 algorithms is done by computing for each of them the radial density of the spatial frequencys coverage and the total flux collected by the sub-apertures. An algebraic expression of the diffraction patterns associated to these configurations is given.