The Programmable Liquid-crystal Active Coronagraphic Imager for the 4-m DAG telescope (PLACID) instrument: installation and commissioning update

TL;DR

The PLACID instrument is a novel, programmable liquid-crystal active coronagraphic imager installed on the 4-m DAG telescope, designed for high-contrast direct imaging with dynamic focal-plane phase mask capabilities, and is nearing on-sky commissioning.

Contribution

This paper reports the installation, integration, and upcoming on-sky commissioning of the world's first active coronagraph system with a programmable spatial light modulator.

Findings

Successful installation and integration of PLACID at DAG telescope.

Upcoming on-sky tests scheduled for early 2026.

Potential for advanced adaptive coronagraphic imaging techniques.

Abstract

The Programmable Liquid-crystal Active Coronagraphic Imager for the DAG telescope (PLACID) instrument is a novel high-contrast direct imaging facility that was recently installed on the new Turkish 4-m DAG telescope. In brief, PLACID consists in a fore-optics coronagraphic intermediate stage platform, installed in-between the TROIA XAO system and the DIRAC HAWAII-1RG focal-plane array. The PLACID instrument was delivered to ATASAM campus facilities in March of 2024, and transported to summit in October of 2024. In February of 2025, the PLACID optical breadboard was craned to the DAG observatory floor, and successfully installed on the optical table of the diffraction-limited Nasmyth platform of the 4-m telescope. Following the official DAG Acceptance milestone in the spring of 2025, Assembly, Integration and Validation (AIV) activities have started in July of 2025, when PLACID was cabled up with all active components fully interfaced and tested for functional integrity. When on-sky by early 2026, PLACID will be the world's first active coronagraph system, fielding a customized spatial light modulator (SLM) acting as a dynamically programmable focal-plane phase mask (FPM) coronagraph from H- to Ks-band. This will provide a wealth of novel options to observers, among which software-only abilities to change or re-align the FPM pattern in function of observational conditions or science requirements. Future features will include non-common path aberrations (NCPA) self-calibration, angular differential imaging (ADI) coronagraphy for binary or triple stars, as well as coherent differential imaging (CDI). We hereby present the PLACID AIV activities that have taken place over the last twelve months, and the next steps for commissioning the instrument internally, and on-sky later this year.