High-contrast imaging at first-light of the GMT: The PDR optical and mechanical design for the GMagAO-X ExAO system and results from the HCAT testbed with an HDFS phased parallel DM prototype

ELTs have the potential for imaging reflected light from habitable rocky planets around M-stars. To address that exciting science we present the PDR level optical-mechanical design for a high-contrast coronagraphic instrument for the 25.4m GMT called GMagAO-X. To meet the strict ExAO fitting and servo error requirement (<90nm rms WFE), GMagAO-X must have 21,000 actuator DM capable of >2KHz update speeds. To minimize wavefront/segment piston error GMagAO-X has an interferometric beam combiner on a vibration isolated table, as part of this 21,000 actuator “parallel DM”. Segment/petal piston errors are continuously sensed by a novel Holographic Dispersed Fringe Sensor (HDFS). In addition to a coronagraph, it has a post-coronagraphic Lyot Low Order WFS (LLOWFS) for NCP. Here we present our successful, externally reviewed (Feb. 2024), PDR optical-mechanical design that satisfies GMagAO-X’s top-level science requirements and is compliant with the GMT instrument requirements/ICDs and only requires COTS parts and 2-5" optics. We have also prototyped the parallel DM and the HDFS phasing sensor on the HCAT testbed. We show initial testbed results from both, on-sky results for HDFS.