Co-phasing of segmented telescopes: A new approach to piston measurements

I. Optical concept

¹ Instituto de Astronomia, UNAM AP 70-264 Cd. Universitaria, 04510 Mexico DF, Mexico
² Area de Optica, Departamento de Fisica Aplicada, Facultade de Fisica, Universidade de Santiago de Compostela, Campus Sur, 15706 Santiago de Compostela, Galicia, Spain e-mail: fagosxbv@usc.es

Corresponding author: V. V. Voitsekhovich, voisteko@astroscu.unam.mx

Received: 23 July 2001
Accepted: 2 October 2001

Abstract

One of the main problems arising in the co-phasing of segmented telescopes is the problem of measurements of the relative pistons among the segments. These measurements become especially complicated when the pistons are in order of wavelength fractions. In this paper we present a new approach relative piston measurements which allows for a high-accuracy reconstruction of small pistons. Our approach is based on the shearing interferometry and compared to existed methods it has the following advantages: a high accuracy of piston reconstruction in presence of high levels of noise is combined with the ability to retrieve the pistons taking into account the segment's aberrations.