Two reconstruction methods for optical interferometry

Details Two reconstruction methods for optical interferometry Two reconstruction methods for optical interferometry

Dec 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004sf2a.conf..163m&link_type=abstract

SF2A-2004: Semaine de l'Astrophysique Francaise, meeting held in Paris, France, June 14-18, 2004. Edited by F. Combes, D. Barret

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Scientific paper

Current optical interferometers are affected by unknown turbulent phases on each telescope. The complex Fourier samples measured by the instrument are thus multiplied by unknown phasers corresponding to the turbulent differential pistons between each couple of telescopes. So, the only unaffected phase information is the closure phase of each coherent sub-array. Instead of considering the closures as the only phase data, we consider that we have more data and more unknowns. More specifically, we construct complex data affected by turbulent pistons, and explicitly incorporate the pistons in the inverse problem. Then, we reconstruct the object by minimizing an original metric in the object and these pistons. To do so, we minimize the metric alternatively in object and phases, i.e. we do several "calibration cycles", each one made of a step in object with a know set of phases and a step in phases with a known object. We have recently designed a metric such that the minimization problem is convex for given pistons while modelling accurately the noise statistics. Here we develop a technique to compute the global minimum of the data likelihood criterion for the phase step, in spite of the fact that the latter is dramatically non unimodal. This is achieved by exploiting the separable structure of the phase metric. We are currently testing our technique on experimental data.

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