Real-time control for the GLINT nulling interferometer

Directly imaging habitable-zone exoplanets and obtaining their spectra is a central goal in exoplanet science, but is extremely challenging due to the high contrasts and small angular separations which must be achieved. Nulling interferometry is a solution which suppresses on-axis starlight through destructive interference such that the star is 'nulled out'. The Guided Light Interferometric Nulling Technology Instrument (GLINT) at the 8.2-meter Subaru telescope performs nulling interferometry using waveguides and couplers within a photonic chip, and will provide generalisable insights that are applicable to future nullers. However, to produce high starlight suppression and deeper nulls, correcting seeing-induced wavefront error is of paramount importance. Here we present the design for the real-time control loop of the GLINT instrument which performs fringe tracking and active fringe modulation to correct wavefront errors. To allow for user interaction, the control loop is encapsulated within a graphical user interface, enabling manual, automatic, and simulated functionality, and it utilises the MILK framework for high speed data acquisition and control.