(ExEP) Coralign: a software package for coronagraphic alignment and calibration (paper)

Coronagraphy is one of the leading technologies for directly imaging exoplanets. To suppress starlight at high contrast, coronagraphic masks must be aligned with extreme accuracy and precision, and model-based wave- front correction algorithms must be given accurate calibration parameters. Manual alignment and calibration of coronagraphic masks is typical in most testbeds, but automation is necessary to guarantee accuracy and repeatability. To meet the strict requirements of NASA’s Nancy Grace Roman Space Telescope Coronagraph Instrument, the Jet Propulsion Laboratory created a unit-tested software package for coronagraphic alignment and calibration. For public release, we made the software more user friendly and added more routines from the High Contrast Imaging Testbed (HCIT) facility. This open-source software package, named Coralign, contains a suite of algorithms for the alignment and calibration of the unmasked beam, deformable mirrors, and several types of coronagraphic masks (e.g., an occulter, vortex, Lyot stop, apodizer, and field stop). Coralign is available in Python (and soon in MATLAB) at github.com/nasa-jpl/coralign.