Design and simulation of non-redundant aperture masks for SCALES

The year 2025 is expected to see the first facility-class integral field spectrograph (IFS) operating in the 2.0 - 5.2um regime come online at the W. M. Keck Observatory. SCALES, which stands for Slicer Combined with an Array of Lenslets for Exoplanet Spectroscopy, will extend the parameter space of exoplanets that can be directly imaged to colder, older planets. SCALES will also image other high-contrast targets such as circumstellar disks, Solar System planets and moons, and supernovae. It is possible to improve upon SCALES’ high-contrast imaging performance by introducing interferometric techniques such as non-redundant aperture masking (NRM). NRM is a cheap-to-implement technique that effectively transforms a telescope aperture into an interferometer. Closure phase and squared visibility are two observables that are obtained from NRM and can be used to nullify systematic noise and reconstruct images with improved spatial resolution. In this work we present the final designs of NRMs selected to be integrated into SCALES. We detail the design process for these masks using the NRM-artist Python package and the techniques used to simulate their performance in mock SCALES data using the scalessim package. Finally, we describe the manufacture, laboratory testing, and integration procedures for the masks.