The Programmable Liquid-crystal Active Coronagraphic Imager for the DAG telescope (PLACID) instrument: simulations, discovery space and status update 

Abstract

We present the Programmable Liquid-crystal Active Coronagraphic Imager for the DAG telescope (PLACID) instrument, a novel exoplanet direct imaging facility that was recently delivered to the Turkish 4-m DAG telescope, with first light anticipated by the end of 2024. In a nutshell, PLACID consists of a fore-optics coronagraphic intermediate stage platform, installed in-between the TROIA XAO system and the DIRAC HAWAII-2RG focal-plane array. The PLACID instrument, led by a consortium of Swiss Universities contracted by the Atatürk University Astrophysics Research and Application Center (ATASAM), was delivered to ATASAM premises in March 2024 and is scheduled for on-telescope installation in the fall of 2024. Once on-sky later this year, PLACID will be the world’s first “active coronagraph” high-contrast imaging facility, fielding a pixelated spatial light modulator (SLM) acting as a dynamically programmable focal-plane phase mask (FPM) coronagraph from H- to Ks-band. We also detail our Python-based numerical simulator of pixelated FPM coronagraphy, built to investigate the effect of SLM-generated FPM patterns in place of classical phase masks. The simulator explores the impacts of various design choices and parameters, such as spatial sampling (SLM pixels per λ/D), phase resolution (greylevel steps) and Lyot stop sizing etc. Overall, the tool enables detailed simulations of PLACID or similar SLM-based instruments, and can support real-time operations (optimal choice of FPM for given observing conditions) and interpretation of real data. Additionally, the tool is designed to evolve in order to integrate and simulate advanced operation modes, in particular focal-plane phase diversity for coherent differential imaging (CDI) of exoplanets. We present the current status of our code, and some early conclusions on the impacts of a few key instrument design parameters. This imminent on-sky commissioning and early science operation of PLACID  will require careful planning in terms of target selection and related observational settings. To this purpose, we present the likely science discovery space for PLACID, in terms of known exoplanets, brown dwarfs and circumstellar disks, considering foreseen adaptive optics performance, achievable coronagraphic contrast, limiting magnitudes, coronagraphic inner working angle, etc. Predicted disk and binary/multiple star systems imaging performance is also investigated, with the latter being a possible niche science case for the instrument, as PLACID can uniquely generate adaptive FPMs to null multiple stars in the field-of-view.