Aperture masking interferometry with ELT-METIS

Abstract

We present sparse-aperture masks for the L/M- and N-band imaging channels of METIS on the ESO ELT. The 6-hole mask forms six ∼4m sub-apertures with Keck-like collecting area and non-redundant baselines for broadband (∼20%) filters. The 12-hole mask forms twelve ∼1.6m sub-apertures, conceptually similar to a VLTI-AT array but with three times as many elements packed into a ∼34m maximum baseline, giving denser uv coverage for narrow-band filters. These masks target self-luminous planets, brown dwarfs, and compact circumstellar structure within ∼0.05–0.1′′, where AO PSF variability and coronagraphic inner working angles limit classical imaging. We summarize final mask geometries, uv coverage, and design methodology, and outline simulations combining HEEPS AO residuals, ScopeSim detector models, and SAMpy extraction. This framework will quantify where masking can compete with or outperform coronagraphy at a few λ/D.