Laboratory testing and calibration of the upgraded MMT adaptive secondary mirror

Amali Vaz; Katie M. Morzinski; Manny Montoya; Chuck Fellows; John Ford; Andrew Gardner; Olivier Durney; Grant West; Lori Harrison; Frank Gacon; Elwood Downey; Jared Carlson; Emily Mailhot; Narsireddy Anugu; Buell Jannuzi; Phil Hinz

doi:10.1117/12.2576352

13 December 2020 Laboratory testing and calibration of the upgraded MMT adaptive secondary mirror

Amali Vaz, Katie M. Morzinski, Manny Montoya, Chuck Fellows, John Ford, Andrew Gardner, Olivier Durney, Grant West, Lori Harrison, Frank Gacon, Elwood Downey, Jared Carlson, Emily Mailhot, Narsireddy Anugu, Buell Jannuzi, Phil Hinz

Author Affiliations +

Proceedings Volume 11448, Adaptive Optics Systems VII; 114485L (2020) https://doi.org/10.1117/12.2576352
Event: SPIE Astronomical Telescopes + Instrumentation, 2020, Online Only

Conference Poster

Abstract

The MMT Adaptive optics exoPlanet characterization System (MAPS) is a broad overhaul and upgrade of AO instrumentation at the 6.5-m MMT observatory, from deformable secondary mirror, through pyramid wavefront sensors in both the visible and near-infrared, to improved science cameras. MAPS is an NSF MSIP-funded program whose ultimate goal is a facility optimized for exoplanet characterization. Here we describe the laboratory testing and calibration of one MAPS component: the refurbished MMT adaptive secondary mirror (ASM). The new ASM includes a complete redesign of electronics and actuators, including simplified hub-level electronics and digital electronics incorporated into the actuators themselves. The redesign reduces total power to ⪅300W, from the original system’s 1800W, which in turn allows us to eliminate liquid cooling at the hub with no loss of performance. We present testing strategies, results, and lessons learned from laboratory experience with the MAPS ASM. We discuss calibrations first on the level of individual actuators, including capacitive position sensing, force response function, and individual closed-loop position control with an improved control law. We then describe investigations into the full ASM system – hub, actuators, thin shell, and human – to understand how to optimize interactions between components for dynamical shape control using a feedforward matrix. Finally, we present our results in the form of feedforward matrix and control law parameters that successfully produce a desired mirror surface within 1ms settling time.

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Amali Vaz, Katie M. Morzinski, Manny Montoya, Chuck Fellows, John Ford, Andrew Gardner, Olivier Durney, Grant West, Lori Harrison, Frank Gacon, Elwood Downey, Jared Carlson, Emily Mailhot, Narsireddy Anugu, Buell Jannuzi, and Phil Hinz "Laboratory testing and calibration of the upgraded MMT adaptive secondary mirror", Proc. SPIE 11448, Adaptive Optics Systems VII, 114485L (13 December 2020); https://doi.org/10.1117/12.2576352

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