The PLACID Active Coronagraph: Commissioning

The Programmable Liquid-crystal Active Coronagraphic Imager for the DAG telescope (PLACID) is the first adaptive coronagraphic instrument designed for direct exoplanet imaging. The term “adaptive” refers to its capability to dynamically re-program the coronagraphic focal-plane phase mask (FPM) in real time, adapting to evolving observing conditions through the use of a customized spatial light modulator (SLM). Operating across the H to Ks spectral bands, the SLM acts as a fully programmable FPM, allowing patterns to be updated or recentered entirely via software without any mechanical motion. This flexibility enables observers to choose from a variety of coronagraphic modes and optimize observations for specific scientific goals or instrument conditions.

PLACID was delivered to the Turkish National Observatories (TNO) at Atatürk University in Erzurum in March 2024. It was subsequently transported to summit and installed on the diffraction-limited Nasmyth platform of the 4-meter Turkish DAG telescope during the first half of 2025, followed by full cabling and successful functional verification by mid-2025.

The instrument is now located at an intermediate coronagraphic fore-optics stage between the TROIA extreme adaptive optics (XAO) system and the DIRAC HAWAII-1RG infrared detector of the DAG telescope. Assembly, Integration, and Validation (AIV) activities on the diffraction-limited Nasmyth platform have progressed significantly, with initial alignment of the TROIA XAO system and DIRAC detector beam path completed by the end of 2025. PLACID itself completed the AIV phase in February of 2026 and is due to pass Preliminary Acceptance by mid-2026, in parallel with the first adaptive optics loop-closing operations. The PLACID first light is anticipated for late summer or early autumn of 2026.

In preparation for initial science operations, the PLACID graphical user interface (GUI) has been finalized. The instrument’s expected discovery space has been evaluated using a combination of laboratory measurements obtained during factory acceptance testing and simulations that incorporate residual wavefront errors after adaptive optics correction. These results have been integrated into an updated exposure time calculator, which accounts for adaptive optics performance, achievable contrast, limiting magnitudes, and the coronagraphic inner working angle. Furthermore, a ground-based observation planning tool has been developed, that will comprehensively assist astronomers in planning high-contrast imaging observations, providing information such as transit/zenith time, moon position, expected airmass, rate of change in parallactic angle and much more.

PLACID’s primary scientific goal is the direct imaging of exoplanets and circumstellar disks in the Northern Hemisphere. A highlight science case aims at targeting compact multiple star systems in search of circumbinary companions or disks, often excluded by high-contrast imaging surveys in the past. To support this, new observing modes are under development to enable coronagraphic imaging of binary and multiple systems in combination with Angular Differential Imaging (ADI). These include implementations such as the binary Roddier & Roddier mask and, more recently, binary vortex masks, representing a novel approach in coronagraphy. The PLACID data reduction pipeline is based on the PynPoint high-contrast imaging framework and is fully prepared for on-sky data processing.

Additional instrument capabilities will be implemented following the first science observations after commissioning in 2026. These planned features include self-calibration of non-common path aberrations using a phase-shifting Zernike wavefront sensor, coronagraphic nulling optimized for binary and triple star systems compatible with ADI, and time-domain coherent differential imaging (CDI).

In this work, we present the PLACID instrument as delivered, along with its predicted discovery space, binary coronagraphy capabilities, observation planning tools, and current on-site status. Initial results from Nasmyth platform commissioning using the internal calibration source, as well as first on-sky performance, if available, will be discussed. The instrument is being prepared for on-sky commissioning in the second half of 2026, with routine science observations expected to begin in 2027.