Fizeau-interferometry fringe tracking solutions for giant segmented telescope petal modes

Frantz Martinache; Nick Cvetojevic; Vincent Deo

doi:10.1117/12.2630546

29 August 2022 Fizeau-interferometry fringe tracking solutions for giant segmented telescope petal modes

Frantz Martinache, Nick Cvetojevic, Vincent Deo

Proceedings Volume 12185, Adaptive Optics Systems VIII; 121851A (2022) https://doi.org/10.1117/12.2630546
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Abstract

General purpose adaptive optics are poorly suited to handling wavefront modes that naturally occur or are amplified by discontinuities introduced by the telescope and its surrounding structure. This limitation, whose devastating effects were revealed by extreme adaptive optics fed high-contrast imaging instruments experiencing low wind effect conditions, is expected to be even more severe for the next generation of giant segmented telescopes (GST) that generally feature numerous stronger discontinuities. Another astrophysical high-angular resolution tool, long baseline optical interferometry, is regularly tackling this problem and is perfectly able to co-phase an array, with sub-precision, even in the presence of large initial piston excursions. One way to solve for the so-called petal-mode problem is to interferometric solutions to the GST scenario. One approach is to use a sparse aperture mask (SAM) in a plane conjugated with the pupil of the telescope and exploit the information present in the resulting Fizeau interferograms. Traditionally, SAM are used for astrophysical purposes, and are therefore part of instruments: the masks are non-redundant (see Deo et al, this conference), which optimizes the Fourier sampling but is not optimized for metrology. This paper introduces a partially redundant mask design that provides better sensitivity to the petal modes, shows how to go from interferograms to a full description of the petal modes using simulations, and looks at how to implement this solution as part of the telescope, possibly even ahead of the adaptive optics, using the European ELT as a study case.

Conference Presentation

Citation Download Citation

Frantz Martinache, Nick Cvetojevic, and Vincent Deo "Fizeau-interferometry fringe tracking solutions for giant segmented telescope petal modes", Proc. SPIE 12185, Adaptive Optics Systems VIII, 121851A (29 August 2022); https://doi.org/10.1117/12.2630546

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