Augmented design for a fully automated alignment system at the Magdalena Ridge Observatory Interferometer

Abstract

Stable beam alignment of an optical interferometer is crucial for maintaining a usable signal-to-noise ratio during science measurements on faint astronomical targets. The Magdalena Ridge Observatory Interferometer will use an Automated Alignment System (AAS) that performs a start-of-night alignment procedure and subsequent alignment corrections in between observations, all without the need for human intervention. Its design has recently been updated in line with a revised error budget for MROI requiring that two axis drifts during science operations should not exceed 15 milliarcseconds in tilt, referred to the sky, nor 1% of the beam diameter in shear. For each beam line, the AAS provides two reference light beams, a pair of quad cells to monitor coarse alignment, and a tilt and shear detector for tracking fine drifts. The tilt and shear detector is a novel application of a Shack-Hartmann array that permits the simultaneous measurement tilt and shear well within requirements for MROI. Results of laboratory testing and simulations are presented here.