Adaptive secondary mirror development for the UH-88 telescope

TNO and industrial partners VDL ETG, L3Harris and Hyperion are developing a novel Adaptive Secondary Mirror (ASM) for Ground Layer Adaptive Optics (GLAO) at the University of Hawaii’s 88-inch telescope on Mauna Kea. The ASM is based on a unique actuator principle which delivers a >30µm PV 99% linear stroke at a very high efficiency in terms of force per unit of volume and of power. The adaptive mirror does not require active cooling and due to its compactness can be fitted within the same volume of the original passive mirror. The overall dimensions of the ASM for the UH88 are o63cm with 204 actuators in a circular grid and an overall height of 13cm. The ULE mirror shell has an aspherical convex shape with a 4,2-meter radius of curvature and a thickness of 3,5mm. At the time of writing of this paper the project is in the critical design phase with installation on the telescope anticipated late 2020.